UBC Theses and Dissertations

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UBC Theses and Dissertations

Studies in the neural control of avian locomotion Sholomenko, Gerald Norman Weinstein 1989

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STUDIES IN THE NEURAL CONTROL OF AVIAN LOCOMOTION By GERALD NORMAN WEINSTEIN  SHOLOMENKO  B.Sc,  The U n i v e r s i t y  of B r i t i s h  Columbia,  1974  M.Sc,  The U n i v e r s i t y  of B r i t i s h  Columbia,  1985  A THESIS SUBMITTED  IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS  FOR  THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE  STUDIES  (NEUROSCIENCE)  We  accept to  this  thesis  the required  as  conforming  standard  THE UNIVERSITY OF BRITISH COLUMBIA M a r c h 1989 ©  G e r a l d Norman W e i n s t e i n  Sholomenko, 198 9  In  presenting  degree freely  this  thesis  in partial  fulfilment  at the University  of British  Columbia,  available  copying  for reference  of this  department publication  or  thesis by  of this  thesis  purposes  her representatives.  for financial  permission.  Department of  A)&tAA>o  S&C6~*C?  The University of British Columbia Vancouver, Canada  DE-6 (2/88)  I agree  and study. I further  f o r scholarly  his o r  of the requirements  gain  agree  may  that that  for an  the Library permission  be granted  shall  make it  for extensive  by the head  It is understood  shall not be allowed  advanced  that without  of  my  copying  or  my  written  ABSTRACT This  s t u d y examines a s p e c t s o f t h e n e u r a l s u b s t r a t e f o r  locomotion hindbrain  i nbirds.  Electrical  stimulation  revealed three previously undefined brainstem  f r o m w h i c h l o c o m o t i o n was e l i c i t e d The  sites  l i e w i t h i n the medial  intercollicular formation  nucleus  i n the decerebrate  longitudinal  at e l i c i t i n g  i n t o t h e MLF, p o n t o b u l b a r reticular  P t o determine  neurotransmitters at these  a g o n i s t s were e f f e c t i v e  locomotor  f o r m a t i o n . NMDA i n j e c t i o n  medullary  reticular  electrical injection  strip  effects  Cholinergic injected  (PLS) a n d m e d u l l a r y locomotion  and m e d u l l a r y  i n t o t h e PLS, MLF, mMRF a n d locomotion  t h r e s h o l d f o r locomotion,  e v o k e d l o c o m o t i o n when i n j e c t e d  formation. Phasic peripheral  n o t t o be e s s e n t i a l locomotor  sites.  l o c o m o t i o n when  formation e l i c i t e d  stimulation  locomotor  t h e locomotor  i n t o t h e PLS, ICo a n d p o n t i n e  reticular  reticular  reticular  GABA, t h e e x c i t a t o r y  f o r m a t i o n . GABAergic a n t a g o n i s t s evoked  when i n f u s e d  (MLF),  the microinjection of  and a n t a g o n i s t s t o a c e t y l c h o l i n e ,  of potential  P  fasciculus  (mMRF). T h e s e a n d p r e v i o u s l y d e f i n e d a v i a n  amino a c i d s a n d S u b s t a n c e  regions  animal.  (ICo) a n d m e d i a l m e s e n c e p h a l i c  r e g i o n s were f u r t h e r e x a m i n e d u t i l i z i n g agonists  o f mid- and  or reduced t h e while  Substance  into the pontine  afferent  i n p u t was f o u n d  f o r t h e p r o d u c t i o n o f an a r r a y o f a v i a n  p a t t e r n s when e x a m i n e d i n t h e s p o n t a n e o u s ,  electrically  s t i m u l a t e d and n e u r o c h e m i c a l l y  p r e p a r a t i o n s . However, a f f e r e n t  feedback  stimulated paralyzed  may have a r o l e i n  setting theactivation  level  frequency  p a t t e r n s . The p r e s e r v a t i o n o f c a u d a l  o f locomotor  required to initiate  diencephalic neural structures  and s e t t h e  a l l o w e d spontaneous locomotion i n ii  the high decerebrate b i r d , lenticularis,  subthalamic  as p o s s i b l y m o d u l a t i n g an  implicating nucleus  lateral  more c a u d a l l o c o m o t o r  i n t e g r a t e d approach with the  variety  and  the nucleus  o f v e r t e b r a t e s , my  literature  results  range.  iii  hypothalamic regions.  in birds  suggest  ansa area  Utilizing  data c o l l e c t e d  l o c o m o t o r - r e l a t e d n e u r a l pathways are h i g h l y broad phylogenetic  of the  from  that  conserved  across a  a  TABLE OF CONTENTS Page Abstract Table of Contents L i s t of Tables L i s t of Figures Table of Abbreviations Acknowledgement Chapter  i i iv viii ix xi xvi  1 - Review o f t h e L i t e r a t u r e Introduction  and G e n e r a l  1  Review o f t h e L i t e r a t u r e S p i n a l Cord Cortex L a t e r a l V e s t i b u l a r N u c l e u s and Tectum Red N u c l e u s R e t i c u l a r Formation L o c o m o t o r R e g i o n s and L o c o m o t i o n - R e l a t e d S t r u c t u r e s Cerebellum P o n t o b u l b a r Locomotor S t r i p M e s e n c e p h a l i c Locomotor Region S u b t h a l a m i c N u c l e u s and S u b t h a l a m i c L o c o m o t o r R e g i o n Basal Ganglia Limbic Structures C o n c l u s i o n s and P u r p o s e o f S t u d i e s i n t h e T h e s i s The D e c e r e b r a t e P r e p a r a t i o n Nomenclature Chapter  2 - E l e c t r i c a l Stimulation of Mesencephalic Pontine Regions E l i c i t s Locomotion i n Decerebrate Birds  Introduction M a t e r i a l s and Methods Figure 3 Results Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Discussion Conclusions  and  2 5 9 11 14 15 18 18 20 23 29 31 32 34 41 46 48  49 52 54 58 59 61 64 67 71 73 79  iv  C h a p t e r 3 - C h a r a c t e r i z a t i o n o f A v i a n M i d - and H i n d b r a i n S i t e s t h a t Produce Locomotion with L o c a l Intracerebral Infusion of Neurotransmitter A g o n i s t s and A n t a g o n i s t s (I): Acetylcholine. Introduction M a t e r i a l s and Methods Results Table 1 Figure 9 F i g u r e 10 F i g u r e 11 F i g u r e 12 F i g u r e 13 F i g u r e 14 Discussion Chapter  81  82 85 88 89 90 92 96 99 101 105 108  4 - C h a r a c t e r i z a t i o n o f A v i a n M i d - and H i n d b r a i n S i t e s t h a t Produce Locomotion with L o c a l Intracerebral Infusion of Neurotransmitter A g o n i s t s and A n t a g o n i s t s (II) : y - A m i n o b u t y r i c A c i d (GABA).  Introduction M a t e r i a l s and Methods Results Table 2 F i g u r e 15 F i g u r e 16 F i g u r e 17 . F i g u r e 18 F i g u r e 19 F i g u r e 20 Discussion  •  C h a p t e r 5 - C h a r a c t e r i z a t i o n o f A v i a n M i d - and H i n b r a i n S i t e s t h a t Produce Locomotion w i t h L o c a l Intracerebral Infusion of Neurotransmitter A g o n i s t s and A n t a g o n i s t s (III): Excitatory Amino A c i d s and S u b s t a n c e P. Introduction M a t e r i a l s and Methods Results Table 3 F i g u r e 21 F i g u r e 22 F i g u r e 23 F i g u r e 24 F i g u r e 25 F i g u r e 26 Discussion  133  134 137 138 139 140 143 145 148 151 154 157 166  167 168 169 170 171 174 176 181 187 191 195  v  TABLE OF CONTENTS (CONTINUED)  Page Chapter 6 - A v i a n Locomotion i n the Absence o f P h a s i c A f f e r e n t Input - The ^ F i c t i v e ' P r e p a r a t i o n Introduction M a t e r i a l s and Methods Results F i g u r e 27 F i g u r e 28 F i g u r e 29 F i g u r e 30 F i g u r e 31 F i g u r e 32 F i g u r e 33 Discussion  208 209 211 213 214 216 219 222 224 226 229 231  Chapter 7 - T r a n s e c t i o n L e v e l Determines Spontaneous Motor A c t i v i t y i n the D e c e r e b r a t e A v i a n P r e p a r a t i o n Introduction Table 4 F i g u r e 34 M a t e r i a l s and Methods Results F i g u r e 35 F i g u r e 36 F i g u r e 37 Discussion  236 237 238 239 241 243 244 24 6 248 253  Chapter 8 - Summary D i s c u s s i o n  258  Chapter 9 - L i s t o f R e f e r e n c e s  273  Appendix I  2 91  Appendix I I  2 94  vi  L I S T OF TABLES Page Table  1 - Time c o u r s e , l a t e n c y and c o n c e n t r a t i o n s o f a c e t y l c h o l i n e a g o n i s t s and a n t a g o n i s t s  89  Table  2 - Time c o u r s e , l a t e n c y and c o n c e n t r a t i o n s o f GABA, i t s a g o n i s t s and a n t a g o n i s t s  139  Table  3 - Time c o u r s e , l a t e n c y and c o n c e n t r a t i o n s o f g l u t a m a t e , i t s a g o n i s t s and a n t a g o n i s t s and S u b s t a n c e P  170  Table  4 - Cat d e c e r e b r a t i o n  238  levels.  vii  LIST OF FIGURES Chapter  1  Figure Figure  1. 2.  Page Diagram o f c a t d e c e r e b r a t i o n l e v e l s . Electromyographic a c t i v i t y , blood pressure and h e a r t r a t e r e s u l t i n g f r o m e l e c t r i c a l s t i m u l a t i o n i n TTD  6 44  Chapter 2 Figure Figure  3. 4.  Figure  5  Figure  6.  Figure  7.  Figure  8.  Diagram o f a v i a n e x p e r i m e n t a l apparatus. Composite diagram o f e l e c t r i c a l s t i m u l a t i o n s i t e s i n pons and m e s e n c e p h a l o n . S t i m u l a t i o n s i t e s on c o r o n a l s e c t i o n s i n t h e avian b r a i n . EMG r e c o r d s o f l o c o m o t i o n e l i c i t e d by MLF stimulation. EMG r e c o r d s o f l o c o m o t i o n e l i c i t e d by mMRF s t i m u l a t i o n and a f f e c t s o f s t i m u l a t i o n frequency. EMG r e c o r d s o f l o c o m o t i o n e l i c i t e d by ICo stimulation.  54 59 61 64 67 71  Chapter 3 Figure  9.  Figure  10  Figure  11  Figure  12  Figure  13  Figure  14  Chapter  Composite diagram o f c h o l i n e r g i c a g o n i s t & antagonist neurochemical i n j e c t i o n s i t e s . S t i m u l a t i o n and i n j e c t i o n s i t e s on c o r o n a l s e c t i o n s i n the avian b r a i n EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and c a r b a c h o l i n j e c t i o n i n t o t h e PLS. EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and c a r b a c h o l i n j e c t i o n i n t o the Cnd. EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and c a r b a c h o l i n j e c t i o n i n t o the Cnv. EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and c a r b a c h o l i n j e c t i o n i n t o the MLF.  90 92 96 99 101 105  4  Figure  15  Figure  16  Figure  17  C o m p o s i t e d i a g r a m o f G A B A e r g i c a g o n i s t and antagonist neurochemical i n j e c t i o n s i t e s . EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and p i c r o t o x i n i n j e c t i o n i n t o t h e PLS. EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d by p i c r o t o x i n and b i c u c u l l i n e i n j e c t i o n i n t o t h e PLS..  viii  14 0 143  145  LIST OF FIGURES  (CONTINUED) Page  Figure Figure Figure  18.- EMG r e c o r d s o f l o c o m o t o r a c t i v i t y e l i c i t e d b y 148 e l e c t r i c a l s t i m u l a t i o n o f t h e PLS b l o c k e d b y GABA i n f u s i o n . 19.- EMG r e c o r d s s h o w i n g G A B A - r e v e r s i b l e locomotor 151 a c t i v i t y e l i c i t e d by p i c r o t o x i n i n j e c t i o n i n t o Cnv. 2 0 . - EMG r e c o r d s s h o w i n g G A B A - r e v e r s i b l e locomotor 154 a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and p i c r o t o x i n i n f u s i o n i n t o RP.  Chapter 5 Figure Figure Figure Figure Figure Figure  2 1 . - C o m p o s i t e d i a g r a m o f EAA. & SubP a g o n i s t a n d antagonist neurochemical i n j e c t i o n s i t e s . 22.- EMG r e c o r d s s h o w i n g l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n a n d NMDA i n j e c t i o n i n t o t h e PLS. 2 3 . - EMG r e c o r d s s h o w i n g G D E E - r e v e r s i b l e m o t o r e l i c i t e d b y e l e c t r i c a l s t i m u l a t i o n a n d NMDA i n j e c t i o n i n t o t h e Cnd. 24.- EMG r e c o r d s s h o w i n g G D E E - r e v e r s i b l e l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n and NMDA i n j e c t i o n i n t o t h e Cnv. 2 5 . - EMG r e c o r d s s h o w i n g l o c o m o t o r a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n , Substance P a n d NMDA i n j e c t i o n i n t o t h e RP. 2 6 . - EMG a n d ENG r e c o r d s s h o w i n g l o c o m o t o r a c t i v i t y e l i c i t e d b y e l e c t r i c a l s t i m u l a t i o n a n d NMDA i n f u s i o n i n t o t h e MLF.  171 174 17 6 181 187 191  Chapter 6 Figure  27.- B i l a t e r a l a l t e r n a t i n g w a l k i n g a c t i v i t y i n a 214 spontaneously locomoting b i r d b e f o r e and a f t e r paralyzation. F i g u r e 28.- H i s t o g r a m o f e l e c t r i c a l s t i m u l a t i o n - i n d u c e d 216 and s p o n t a n e o u s s t e p f r e q u e n c y during p r e - p a r a l y z e d and p a r a l y z e d ^ f i c t i v e ' s t e p p i n g . F i g u r e 29.- B i l a t e r a l a l t e r n a t i n g w a l k i n g a c t i v i t y evoked 219 by f o c a l e l e c t r i c a l s t i m u l a t i o n o f t h e h i n d b r a i n b e f o r e and a f t e r p a r a l y z a t i o n . F i g u r e 30.- C o - a c t i v a t i o n o f l e g a n d w i n g a c t i v i t y e v o k e d 222 by f o c a l e l e c t r i c a l s t i m u l a t i o n o f t h e midbrain b e f o r e and a f t e r p a r a l y z a t i o n . F i g u r e 31.- B i l a t e r a l s y n c h r o n o u s f l y i n g a c t i v i t y e v o k e d 224 by f o c a l e l e c t r i c a l s t i m u l a t i o n o f t h e h i n d b r a i n b e f o r e and a f t e r p a r a l y z a t i o n . F i g u r e 32.- H i s t o g r a m o f e l e c t r i c a l s t i m u l a t i o n - i n d u c e d 226 wingbeat frequency d u r i n g p r e - p a r a l y z e d and paralyzed *fictive' flapping. ix  LIST OF FIGURES (CONTINUED)  Page F i g u r e 33.- B i l a t e r a l * f i c t i v e ' h i n d l i m b a c t i v i t y e l i c i t e d by m i c r o i n j e c t i o n o f c a r b a c h o l and NMDA i n t o t h e pons and m e d u l l a .  229  Chapter 7 F i g u r e 34.- Diagram o f a s a g g i t a l s e c t i o n through' t h e c a t b r a i n s t e m showing n e u r a x i s t r a n s e c t i o n l e v e l s and locomotor s i t e s i m p o r t a n t t o motor c o n t r o l . F i g u r e 35.- Diagram o f t r a n s e c t i o n l e v e l s o f t h e a v i a n b r a i n which p e r m i t o r e l i m i n a t e spontaneous locomotion i n the decerebrate b i r d . F i g u r e 36.- B i l a t e r a l a l t e r n a t i n g w a l k i n g a c t i v i t y i n a s p o n t a n e o u s l y l o c o m o t i n g b i r d b e f o r e and a f t e r paralyzation. F i g u r e 37.- EMG r e c o r d s showing spontaneous s t e p p i n g and f l y i n g a c t i v i t y i n a high decerebrate b i r d .  x  239 244 246 24 8  TABLE OF ABBREVIATIONS  ACh AChE AChM AChN AHP AL AM Anl ANOVA APH AQ ATRO AVT  acetylcholine acetylcholinesterase acetylcholine muscarinic receptor acetylcholine n i c o t i n i c receptor area hypothalami p o s t e r i o r i s ansa l e n t i c u l a r i s nucleus a n t e r i o r medialis hypothalami nucleus annularis analysis of variance area parahippocampalis c e r e b r a l aqueduct atropine area v e n t r a l i s o f Tsai  BC BICUC BO b.p.  brachium conjunctivum bicuculline olfactory bulb blood pressure  CA CARB Cb CC . CCK CCU CCV CF ChAT CHCS CM CNS Cnd Cnv CO CoS CP CPG CS CT CI C2 C3 C4  a n t e r i o r commissure c a r b a c h o l (carbamyl c h o l i n e ) cerebellum central canal cholecystokinin constant current unit v e n t r a l c e r e b e l l a r commissure cuneiform nucleus choline acetyltransferase corticohabenular and c o r t i c o s e p t a l t r a c t m a m m i l l a r y body c e n t r a l nervous system dorsal part, c e n t r a l nucleus o f medulla ventral, part, c e n t r a l nucleus of medulla o p t i c chiasm s e p t a l commissural nucleus p o s t e r i o r commissure c e n t r a l p a t t e r n generator (rhythmic o s c i l l a t o r ) c e n t r a l s u p e r i o r n u c l e u s (Betcherew) t e c t a l commissure c e r v i c a l s p i n a l c o r d segment 1 . c e r v i c a l s p i n a l c o r d segment 2 c e r v i c a l s p i n a l c o r d segment 3 c e r v i c a l s p i n a l c o r d segment 4  DBC DLF DM DMA DMP DSCT  decussation o f the brachium conjunctivum d o r s o l a t e r a l funiculus spinal cord d e l t o i d e u s major muscle dorsomedial a n t e r i o r thalamic nucleus dorsomedial p o s t e r i o r thalamic nucleus dorsal spinocerebellar tract  xi  DSD DSV  supraoptic dorsal decussation supraoptic ventral decussation  EAA EM  e x c i t a t o r y amino a c i d s ( g l u t a m a t e , ectomammillary nucleus electromyogram electroneurogram Edinger-Westphal nucleus  EMG ENG  EW FCL FD FLM FRA FRL FRM FTL  FV GABA GABAA  GC GCt GDEE HA  Hb Hp HRP  HV Hz IC ICo INC 10  aspartate)  f l e x o r c r u r i s l a t e r a l i s muscle dorsal funiculus medial l o n g i t u d i n a l f a s c i c u l u s flexor reflex afferent l a t e r a l mesencephalic r e t i c u l a r formation medial mesencephalic r e t i c u l a r formation l a t e r a l tegmental field ventral funiculus y-aminobutyric a c i d GABAA r e c e p t o r subtype c u n e a t e and g r a c i l e n u c l e i c e n t r a l gray glutamic acid diethyl ester hyperstriatum accessorium habenular nucleus hippocampus horseradish peroxidase hyperstriatum ventrale hertz (cycles/second)  i . v.  inferior colliculus nucleus i n t e r c o l l i c u l a r i s i n t e r s t i t i a l nucleus of C a j a l i n f e r i o r o l i v a r y neucleus interpeduncular nucleus nucleus isthmi, pars p a r v o c e l l u l a r i s i l i o t i b i a l i s c r a n i a l i s muscle ( s a r t o r i u s intravenous  KC1  potassium  LC  locus ceruleus supreme f r o n t a l l a m i n a h y p e r s t r i a t a l lamina l a t e r a l hypothalamic area l e f t i l i o t i b i a l i s muscle d o r s a l medullary lamina l a t e r a l mesencephalic locomotor locomotion l a t e r a l p r e o p t i c area l e f t p e c t o r a l i s muscle locomotor p a t t e r n generator p a r o l f a c t o r y lobe  IP  Ipc ITC  LFM LH LHA LITC LMD  1MLR LOCO LPA LPECT LPG LPO  muscle)  chloride  xii  region  (see  CF)  LVN LRF  l a t e r a l v e s t i b u l a r nucleus (Dieters' Nucleus) parvocellular (lateral) r e t i c u l a r formation  M MesV MLd MLF MLR mM mMLR mMRF MNV MPv MRF MUSC MV MW  molar m e s e n c e p h a l i c t r i g e m i n a l n u c l e u s (see MNV) l a t e r a l mesencephalic nucleus, dorsal part medial l o n g i t u d i n a l f a s c i c u l u s mesencephalic locomotor region millimolar m e d i a l m e s e n c e p h a l i c l o c o m o t o r r e g i o n (see PPN) medial mesencephalic r e t i c u l a r formation m e s e n c e p h a l i c t r i g e m i n a l n e r v e n u c l e u s (see MesV) mesencephalic nucleus, pars profundus mesencephalic r e t i c u l a r formation muscimol motor t r i g e m i n a l n u c l e u s m o l e c u l a r weight  N NA nAL NC neurochemical NICO NR nipride NMDA NIII NV NVI NX NXII  neostriatum n u c l e u s accumbens s u b t h a l a m i c n u c l e u s (named n u c l e u s o f t h e a n s a l e n t i c u l a r i s i n birds) caudal neostriatum a neurotransmitter, i t s agonist orantagonist nicotine no r e s p o n s e sodium n i t r o f e r r i c y a n i d e N-methyl-D-aspartate occulomotor nerve t r i g e m i n a l nerve abducens nerve vagus nerve hypoglossal nerve  01 OMd OMv OT Ov  i n f e r i o r o l i v a r y n u c l e u s (see 10) d o r s a l part, occulomotor nucleus v e n t r a l part, occulomotor nucleus o p t i c tectum ovoid nucleus  P P PaM PDA PECT PH PICRO PILO PLS PMH PMI POA POM PPN  p i n e a l ( F i g u r e 32 o n l y ) pons paramedian nucleus cis-2,3-piperidine carboxylate p e c t o r a l i s muscle plexus o f Horsley picrotoxin pilocarpine pontobulbar locomotor s t r i p p o s t e r i o r part, p o s t e r i o r hypothalamic nucleus paramedian i n t e r n a l t h a l a m i c nucleus a n t e r i o r preoptic nucleus medial p r e o p t i c nucleus p e d u n c u l o p o n t i n e n u c l e u s (see mMLR)  xiii  PRESTIM PRF PrV PT PVM  previous t o stimulation pontine r e t i c u l a r formation p r i n c i p l e t r i g e m i n a l sensory nucleus p r e t e c t a l nucleus p e r i v e n t r i c u l a r magnocellular nucleus  R R Rgc RGC RITC RL RP RPECT RPgc Rpc RPC RPO Ru  raphe n u c l e u s r e d n u c l e u s ( F i g u r e s 1 & 31 o n l y ) g i g a n t o c e l l u l a r r e t i c u l a r formation medullary g i g a n t o c e l l u l a r r e t i c u l a r nucleus r i g h t i l i o t i b i a l i s c r a n i a l i s muscle l a t e r a l r e t i c u l a r nucleus caudal pontine r e t i c u l a r formation nucleus r i g h t p e c t o r a l i s muscle g i g a n t o c e l l u l a r part, pontine r e t i c u l a r nucleus pontine nucleus, p a r v o c e l l u l a r part caudal pontine r e t i c u l a r nucleus pontine r e t i c u l a r nucleus, o r a l part red nucleus  S SC SCE SCI SCOP SG SGC SI SL SLR SM SN SNc SP SpL SRCT SSP ST STIM SV  s o l i t a r y nucleus superior c o l l i c u l u s external c e l l u l a r stratum i n t e r n a l c e l l u l a r stratum scopolamine substantia gelatinosa c e n t r a l gray stratum s u b s t a n t i a innominata l a t e r a l septal nucleus subthalamic locomotor region medial septal nucleus substantia nigra s u b s t a n t i a n i g r a , p a r s compacta subpretectal nucleus l a t e r a l s p i r i f o r m nucleus spinoreticulocerebellar tract supraspinal nucleus subtrigeminal nucleus stimulation t r i g e m i n a l sensory nucleus  T TFS Th TO TPc TSM TTD TU  t r a p e z o i d body trigeminal field stimulation thalamus olfactory tubercle s u b s t a n t i a n i g r a , p a r s compacta (named n u c l e u s tegmentipedunculopontinus i n birds) septomesencephalic t r a c t d e s c e n d i n g t r i g e m i n a l t r a c t and n u c l e u s tuberal nucleus  UDV  unidirectional ventilation  xiv  V VeD VeL VeM VIP vm VS VSCT VTA  ventricle descending v e s t i b u l a r nucleus l a t e r a l v e s t i b u l a r n u c l e u s (see LVN) medial v e s t i b u l a r nucleus vasoactive intestinal polypeptide ventromedial i n t e r n a l c e r e b e l l a r nucleus t r i g e m i n a l s e n s o r y n u c l e u s (see PrV) ventral spinocerebellar tract v e n t r a l tegmental area of T s a i  WGA-HRP  wheat germ a g g l u t i n i n h o r s e r a d i s h p e r o x i d a s e  ZI  zona  III IV VI VII X  o c c u l o m o t o r n e r v e and n u c l e u s t r o c h l e a r nucleus abducens n u c l e u s f a c i a l nucleus d o r s a l motor n u c l e u s vagus  ATH J'TH  increased e l e c t r i c a l decreased e l e c t r i c a l  uA ul uM  microamp microliter micromolar  incerta  xv  threshold threshold  f o r locomotion f o r locomotion  ACKNOWLEDGEMENT & ENDORSEMENT There through  a r e many p e o p l e the t r i a l s  who t o o k p a r t i n h e l p i n g me make i t  and t r i b u l a t i o n s  writing the thesis,  d o i n g t h e comprehensives  forward t o the completion indispensible. support,  caught  birds,  kept  t h a n k y o u enough. S t e p h a n i e ,  the  reading the thesis  future. Polly  f o r your u n f a i l i n g v e r y much! O t h e r s I would l i k e for  all  this  difficult  time,  giving  P, y o u have b e e n u n q u e s t i o n a b l y  moral  c o n f i d e n c e i n my a b i l i t y also helped  to finish.  i n the completion  and t h e i r v e r y h e l p f u l who t a u g h t  Thank y o u  of this  thesis.  Phillips  comments.  me t h a t  into  indispensible  t o t h a n k D r . S t e v e V i n c e n t and D r . Tony  Special  independence  f o r s u c c e s s . Thanks a l s o t o D i e r d r e W e b s t e r , f o r  the coffee,  t h e neuroanatomy and j u s t  t h e g e n e r a l good  n a t u r e d a t t i t u d e w h i c h a l w a y s makes me f e e l people  I  a n d k e e p i n g me on a s t r a i g h t and  go t o D r . J o h n S t e e v e s ,  essential  moral  you d i d n ' t c a t c h b i r d s , b u t  I hope t o t h a n k y o u f o r a l o n g t i m e  reading the thesis  thanks is  t h e s i s w i t h a f i n e t o o t h comb. Greg,  d i d l i v e w i t h me t h r o u g h even l i n e .  gave  h i s good n a t u r e d way e v e n when I  cannot  generally  pushing  were  G r e g Funk h e l p e d w i t h t h e e x p e r i m e n t s ,  and r e a d t h i s  support,  and s i m p l y  o f a Ph.D. S e v e r a l p e o p l e  didn't you  o f doing the experiments,  deserve  t o be h e r e  also.  g o o d . Many o t h e r  They i n c l u d e F r a n k  I g n a c i o V a l e n z u e l a , M a r i a n n e Morgan a n d B i l l  Smith,  M i l s o m . Thank y o u  all! ENDORSEMENT It benefit  i s my w i s h from  that  the publication  t h i s work i n s u p p o r t similarly  no a g e n c y s h o u l d e v e r d e r i v e m i l i t a r y  of their  the a v a i l a b i l t i y  of this  t h e s i s . Authors  who  cite  own a r e r e q u e s t e d t o q u a l i f y  of their  xvi  results.  CHAPTER 1  REVIEW OF THE LITERATURE  AND  GENERAL INTRODUCTION  1  REVIEW OF THE  Over t h e  last  approximately  LITERATURE  100  years  techniques  have b e e n b r o u g h t t o b e a r on  peripheral  nervous systems e x e r t  muscles which are techniques nervous  as  simple  as t h e  function  or outputs  techniques  may  b o t h e l u c i d a t e and  complicate,  the  neurotransmitters  nervous  receptor  u s e d by  about t h e  those  in relation  of  a good d e a l  of  those  the  regions.  eliminate  to delineate regional a v a r i e t y of  amount o f i n f o r m a t i o n will  which  undoubtedly  o f t h e mechanisms o f m o t o r c o n t r o l  localization  the  g i v e us  of  and  s t i m u l a t i o n has  their  to other  regarding  and  neuronal  the  postsynaptic  evoke l o c o m o t o r  populations  patterns  receptors  elucidated several  s p e c i e s . E x t r a - and  firing  their  information  n e u r o n s and  from s e l e c t e d n e u r o n a l  cells  but  w h i c h , when s t i m u l a t e d ,  information  parts  used to  immunocytochemistry  a v a r i e t y of vertebrate  recording  skeletal  removal. Nevertheless,  s u c h as  Focal e l e c t r i c a l  regions  still  and  system.  autoradiography  neurotransmitters  in  with  of various  effort  obfuscate,  Powerful techniques  targets.  i n an  understanding  central  Originally,  c o n t r o l l e d by  have g e n e r a t e d a v a s t  the  s u b s e r v e d by  brain  being  following selective  new  with  isolation  i n v e s t i g a t o r s with  a b o u t what was  inputs  the  c o n t r o l over the  or a b l a t i o n experiments are  certain  how  e f f e c t o r s o f movement.  system p r o v i d e d  information Lesion  the  a v a r i e t y of  patterns  intracellular  provides  phase r e l a t i o n s h i p s o f populations  in  addition to e s t a b l i s h i n g hodological r e l a t i o n s h i p s , while retrograde  and  anterograde neuroanatomical t r a c i n g  2  techniques  have i n c r e a s e d neural  circuits  from the t o be the  the to  the  r e q u i r e the  essentially  spinal cord  of the  locomotor behaviours.  hierarchical, and  being  r e f l e x where o n l y of the  two  neurons,  monosynaptic r e f l e x  motor b e h a v i o u r mechanical fibres).  s u c h as  stimulus  occurs  (e.g.  can  complex nuclei for  the  level of the  and  or  1,  spinal circuitry  intrafusal  also occur  or p a t t e r n  simple  simple  at  muscle  spinal  (spinal  generator)  which  limbs.  The  most  i s found w i t h i n  and  between  f o r e b r a i n which are ( i . e . goal-directed)  responsible locomotion  of c e n t r a l  n e c e s s a r y t o examine s e v e r a l  used i n the  page 6 ) . H i s t o r i c a l l y ,  motor f u n c t i o n o f d i f f e r e n t  in  stimuli.  hierarchical organization  i t is first  types of preparation  neural  of  most  of the  s p i n a l neurons  internal  d i s c u s s i n g the  motor s t r u c t u r e s ,  the  mid-  c o n t r o l of v o l i t i o n a l  Before  Figure  can  o f motor o r g a n i z a t i o n hind-,  level  subserve a r e l a t i v e l y  t o p r o d u c e r h y t h m i c mov.ement o f t h e  response to e x t e r n a l  the  the  s t r e t c h i n g of the  locomotor rhythmic o s c i l l a t o r interact  level  their  is  f o r e b r a i n . The  i n response to a  l e v e l s v i a networks of i n t r i n s i c  which  to perform  complex a t t h e  at the  More complex o r g a n i z a t i o n  remains  organization  comprising  arc,  deal  i n t e g r a t i o n of  neuraxis  i n the  r u d i m e n t a r y motor r e s p o n s e o c c u r s  made c l e a r  mechanisms by  and  The  least  most complex  attendant  locomotion.  organization  components a t a l l l e v e l s  be  a great  p a t h w a y s and  c e n t r a l nervous system c o n t r o l s  normal range o f  will  l i t e r a t u r e below,  elucidated regarding  neural  p a t h w a y s and  s u r p r i s i n g numbers. As  summary o f t h e  Vertebrates  the  number o f d e s c r i b e d  study  studies levels  3  o f motor c o n t r o l  attempting  of the  of (see  to  elucidate  neuraxis  initially  utilized to  selective  removal o r p a r t i t i o n  examine any d e f i c i t s  the  loss of this  1975; that  o f motor c a p a b i l i t y  neural  circuitry  Wetzel and S t u a r t ,  Grillner,  and,  1975),  Figure  (Grillner,  chronic preparations, line  was  f o l l o w i n g surgery.  (see F i g u r e  thalamus  intact  that  In t h e i r  preparation)  stimulation (Bard caudal  third  bodies  using  (Figure 1 and r a b b i t s  i fa transection  portion of  and d i s p l a y b e h a v i o u r s  which  (thalamic  C ) , however, p r o d u c e d a n i m a l s  1924). L a t e r  strong  animals with  locomote spontaneously.  o f the neuraxis  from t h e r o s t r a l  t o the caudal  D)  4  cats e v e n more  However,  border o fthe  b o r d e r o f t h e mammillary  post-mammillary  (Figure 1 - l i n e  which  exteroceptive  studies i n chronic  1958) d e m o n s t r a t e d t h a t  (pre-collicular  preparation)  (1930),  preoptic preparation), the  and locomoted o n l y w i t h  superior colliculus  locomotor  t o the optic  o f t h e thalamus i n t a c t  transections could  transection  preparation,  1975)  a c t i v i t i e s . Brainstem t r a n s e c t i o n leaving  (Laughton,  a n d Macht,  C) c a t s  B), leaving a r o s t r a l  ( F i g u r e 1, l i n e  were more r i g i d  even t h a l a m i c  superior colliculus  a n i m a l s would walk s p o n t a n e o u s l y  only the caudal  e t al.  1900  1975) ( s e e  t o i n t e r r u p t spontaneous  (pre-collicular  resembled motivated  1900, c f . G r i l l n e r ,  (Figure 1 - l i n e  1 - line  (Bickel,  ( G o l t z , 1892 c f . G r i l l n e r ,  reported  made f r o m t h e r o s t r a l  chiasm  (Bickel,  including fish  1975). Indeed, H i n s e y  B) a n d h y p o t h a l a m i c  walked  (cerebral cortex  i n species  1, l i n e A) d i d l i t t l e  behaviours  which r e s u l t e d from  1976) . A number o f i n v e s t i g a t o r s f o u n d  frogs  s u b - p r i m a t e mammals  of the brain  (for review see G r i l l n e r ,  ablation of the telencephalon  decorticate preparation) cf.  of portions  or mesencephalic  (Hinsey  e t a l . , 1930; O r l o v s k y  and  Shik,  1976)  The  e l i m i n a t e d any  above p r e p a r a t i o n s ,  below, have e n a b l e d more e a s i l y  of the  which w i l l  be  c o n t r o l l a b l e c o n d i t i o n s . The  1  locomotion. d i s c u s s e d more  i n v e s t i g a t o r s t o examine l o c o m o t i o n  performed include, electrical  spontaneous  various  f o r example, e l i c i t i n g  2 o r neurochemical  levels  a n i m a l s and  of the  locomotion  neuraxis  below the  the  Spinal  regarding  a great  c o n t r o l of locomotion  exerted  deal by  isolating  Freusberg  (1874), F r e u s b e r g  (1910) were t h e  first  components o f t h e  and  to study  Goltz  (1874)  motor performance  motor s y s t e m . A f t e r h i g h  cord t r a n s e c t i o n or d e c a p i t a t i o n , they  found t h a t  spinal  c a t s and  1 Selective channels  electrical  located  review  on  see  postsynaptic  stimulation  any  Hille,  portion 1984),  presumably  of  and  a  neuron  affects  (e.g.  therefore  may  voltage  terminal,  effect  a  sensitive  axon,  host  cell  of  pre-  body) and  changes.  2 Injection  of  neurotransmitters,  (neurochemicals), receptors 1981).  for  injection  which  the is  the  basis  both,  of  factors  and of  the  not  the  are  efficacious  the  the  is  least neural  (for  changes of  to  autoradiographic  which  acts  which is  and  antagonists  specific  review,  see  footnote),  localize The  neurotransmitter Carpenter  the  it  receptor  selectivity  localization  of  of  and  Reese,  i s possible, sites  at  neurochemical  neurotransmitter  presynaptically, postsynaptically, it elicits  receptor  receptor  the  previous  effective.  neurochemical  neurochemical-induced upon  (see  in  neurochemicals,  antagonist for  agonists  changes  stimulation  receptor  the  their  effect  selected or  Whether  or  dependent  of  agonist  receptors.  they  electrical  using  effects  presumably  which  Unlike  binding  the  Cord  Sherrington  (for  of  system.  Historically,  by  in  transection during controlled  information  nervous  regions  e x a m i n i n g motor r e l a t e d s t r u c t u r e s at  Such s t u d i e s have p r o v i d e d  and  by  . stimulation of s p e c i f i e d  locomotor behaviours.  central  under  manipulations  b r a i n , examining spontaneous locomotor p a t t e r n s  paralyzed  fully  are  subtype.  dependent In  vivo,  on the  a c t i v a t i o n / i n a c t i v a t i o n are  circuitry.  5  a  variety  downstream  dogs  F i g u r e 1. D i a g r a m o f a s a g g i t a l s e c t i o n t h r o u g h t h e c a t b r a i n s t e m showing n e u r a x i s t r a n s e c t i o n l e v e l s and l o c o m o t o r s i t e s i m p o r t a n t f o r the study of locomotor c o n t r o l . T r a n s e c t i o n l e v e l s are d e s i g n a t e d b y l e t t e r s A-E. T r a n s e c t i o n l e v e l : A - t h a l a m i c , B p r e c o l l i c u l a r p r e m a m m i l l a r y ( h y p o t h a l a m i c o f H i n s e y e t al., 1930), C - p r e c o l l i c u l a r postmammillary, D - p r e c o l l i c u l a r p o s t - o c c u l o m o t o r , E - m i d c o l l i c u l a r p r e - o c c u l o m o t o r . Locomotor s i t e s i n c l u d e t h e s u b t h a l a m i c l o c o m o t o r r e g i o n (SLR) a n d m e s e n c e p h a l i c l o c o m o t o r r e g i o n (MLR). The h a t c h e d l i n e s s u r r o u n d i n g RPC a n d RGC r e p r e s e n t t h e p o n t i n e and m e d u l l a r y r e t i c u l a r f o r m a t i o n t h a t a r e t h o u g h t t o be t h e m a j o r m o t o r i n f o r m a t i o n p r o j e c t i o n s y s t e m s t o t h e s p i n a l c o r d . A b b r e v i a t i o n s : CM - m a m m i l l a r y b o d y , CO - o p t i c c h i a s m , I C - i n f e r i o r c o l l i c u l u s , MLR - m e s e n c e p h a l i c l o c o m o t o r r e g i o n , P - p o n s , R - r e d n u c l e u s , RGC - m e d u l l a r y g i g a n t o c e l l u l a r r e t i c u l a r n u c l e u s , RPC - c a u d a l p o n t i n e r e t i c u l a r n u c l e u s , SC - s u p e r i o r c o l l i c u l u s , SLR - s u b t h a l a m i c l o c o m o t o r r e g i o n , T - t r a p e z o i d body, Th - t h a l a m u s , I I I - o c c u l o m o t o r n e r v e . See t e x t f o r a d d i t i o n a l e x p l a n a t i o n . T h i s f i g u r e i s r e d r a w n f r o m : 1) S h i k e t a l . , 1968, 2) O r l o v s k y , 1970a, 3) G r i l l n e r a n d S h i k , 1973 a n d 4) W e t z e l a n d S t u a r t , 1976.  6  continued  to step  i n a rhythmic  stepping" provided supraspinal  the  first  a l t e r n a t i n g manner. T h i s  direct  i n f l u e n c e s were n o t  evidence  essential  Sherrington  that  was  a c t i v a t e d by  peripheral  (1911) d i s p r o v e d previously  this  (sensory)  suggestion  d e a f f e r e n t e d animals  movements f o l l o w i n g s p i n a l (1914) h y p o t h e s i z e d a c t s as spinal  an  intrinsic  stepping  oscillating the  rhythmic  dependent  on  demonstrating  a l s o performed  that a neural  circuit  rhythm o s c i l l a t o r  o s c i l l a t o r s 'of o t h e r  r h y t h m was  p o s t u l a t e d t o be  interconnections  actions  Graham-Brown that  stepping  w i t h i n the  capable  postulated to  limbs  an  spinal  of a n t a g o n i s t i c nerve c e l l s  the  interact  with  rhythmic  (Grillner,  property  cord  The  to produce the  intrinsic  later  of producing  c o o r d i n a t e d movements o f l o c o m o t o r p r o g r e s s i o n The  reflex  (half-centre hypothesis).  o f e a c h l i m b was  of  suggested  c o r d t r a n s e c t i o n . Graham-Brown  i n each limb  circuit  (1910)  i n p u t . However, by  intact  f o r the production  the b a s i c p a t t e r n of locomotion. p o s t - t r a n s e c t i o n locomotion  that  "spinal  of  1975). the  (Graham Brown,  1914) . More r e c e n t l y , G r i l l n e r that  Zangger  (1979)  demonstrated  a s p i n a l - t r a n s e c t e d p a r a l y z e d cat which i s devoid  rhythmic  of  p e r i p h e r a l feedback would a l s o produce p a t t e r n s  a l t e r n a t i n g motor a c t i v i t y efferents.  The  abbreviations fictitious the  and  see  pages  "fictive"  same p a t t e r n as t h e  (unparalyzed)  recorded  electroneurograms list,  or  as  ( P e r r e t e t a l . , 1972)  locomotion.  generalized to a variety  (for  recorded  ENGs r e c o r d e d Although  during  the  of vertebrates  7  of  from p e r i p h e r a l nerve  (ENGs)  xi-xv)  any  complete during  such  locomotion  showed  normal  above f i n d i n g s have b e e n (for review  see  McClellan, stepping'  1986), can  (Eidelberg, the an  occur  1981)  absence of increased  supraspinal  x  f o r the  yet  i n the  t o be  adult  . Several  demonstrated that  o f any  primate  ( E i d e l b e r g et  e t al.  al.,  generators  circuits  that,  on Grillner,  in  primates,  i n f l u e n c e s are  t o t r i g g e r output  that  r e s u l t s from  1981a/b;  (1981a) p o s t u l a t e d  descending t o n i c f a c i l i t a t o r y  pattern  spinal  species  i n adult primates  dependency o f s p i n a l s t e p p i n g influences  x  i n v e s t i g a t o r s have h y p o t h e s i z e d  s p i n a l stepping'  1975). E i d e l b e r g increased  i t has  necessary  from s p i n a l  motorneurons. Despite primates, that  the  inability  t o demonstrate  spinal cord pattern  are  generators  capable of producing  the  ^spinal stepping' (rhythmic  oscillators)  rhythmic a l t e r n a t i n g output  n e c e s s a r y t o evoke l o c o m o t o r a c t i v i t y  have b e e n f o u n d i n a l l  lower v e r t e b r a t e s  1975;  Spinal the  lesion  neural  localized  examined  studies  circuits to  as  Grillner  few  The  and  as  2-3  t o be  fully  are  locomotion  ( S h e f c h y k and  postulated  that  descending  from s u p r a s p i n a l  afferents pattern  generators  characterized  (Grillner,  Jordan,  described  descending  generators  can  the  that  be  circuits  (Cohen and  Wallen,  1979).  flexor reflex  first  1986).  cat demonstrate  u n d o u b t e d l y m o d u l a t e d by  co-workers  interneuron  and  McClellan,  s p i n a l segments, b u t  Zangger,  generators  feedback d u r i n g  lamprey  which comprise the  t h e m s e l v e s have y e t 1980;  (Grillner,  i n the  in  1975). Indeed,  1985;  Jordan,  afferents  l e v e l s may by  a p p e a r t o be  (FRA)  1986)  the  8  Jordan  pathways  i m p i n g e on  a common  regions  and  have  and  Jankowska e t al.  from s u p r a s p i n a l  peripheral  (1967) . However,  to the  major c o n t r o l l i n g  spinal  cord  factor for  the  initiation  1 9 8 2 ) . The  and  ongoing  control  supraspinal nuclei  c o n t r o l which p r o v i d e d i r e c t spinal  cord i n c l u d e the  nucleus, review  tectum  thought  t o be  descending  1982;  connections to  & medullary  Holstege  (Kuypers,  i n v o l v e d i n motor  cortex, red nucleus,  and p o n t i n e  see K u y p e r s ,  of locomotion  lateral  reticular  & Kuypers,  the  vestibular  formation (for  1988).  Cortex  Telencephalic in  structures  m o t i v a t i o n a l or v o l i t i o n a l  responses  (Wetzel  and  a r e known t o be  commands w h i c h e l i c i t  locomotor  S t u a r t , 1 9 7 6 ) . I n mammals, t h e  and motor c o r t e x o f t h e p r e c e n t r a l descending  directly involved  corticospinal  gyrus  gives rise  neurons of the pyramidal  premotor to  system  (Kuypers,  1982). S t i m u l a t i o n o f p a r t s o f t h e motor c o r t e x  discharge  i n motoneurons i n n e r v a t i n g b o t h p r o x i m a l  limb muscles evidence  (Marsden et  suggests  that  al.,  1981;  these d i r e c t  a r e c o n s i d e r a b l y more i m p o r t a n t m u s c l e movements o f t h e d i s t a l of  the proximal  patterns  Kuypers,  distal  1 9 6 4 ) . However,  corticospinal  to the h i g h l y  connections  fractionated  e x t r e m i t i e s than to c o n t r a c t i o n s  limb muscles e s s e n t i a l  (e.g. walking)  and  elicit  (Lawrence and  to basic Kuypers,  locomotor 1968a,b;  Kuypers,  1982) . High  intensity  n e u r o n s has  portion  stimulation  b e e n shown o n l y t o d i s r u p t  1972a), w h i l e increase  electrical  stimulation  flexor of the  at lower  or extensor step cycle  locomotion  tract  (Orlpvsky,  current strengths served to  activity  during the appropriate  ( S h i k e t al.,  9  of pyramidal  1966;  Orlovsky,  1972a;  for  review see Armstrong,  level  of the caudal  locomotion ability  (Lawrence and K u y p e r s ,  of the l a t e r a l  1981). A l s o ,  S t e e v e s and J o r d a n  cat preparation  (mesencephalic locomotor region  postmammillary  cat, the i n i t i a t i o n  rostral  that  stimulation  medullary  of pontine  are antidromically  (Shik  e t al.,  indicate that  initiation  pyramidotomy.  corticofugal fibres t o the r e t i c u l a r  1972a),  elicited  by c o m p l e t e d e s t r u c t i o n  or m i d - c o l l i c u l a r t r a n s e c t i o n  findings  stimulation  a c t i v a t e d by t h e e l e c t r i c a l  1968; O r l o v s k y ,  l o c o m o t i o n w h i c h c o u l d be b l o c k e d MLR  o f l o c o m o t i o n by  t o t h e l e s i o n , which send c o l l a t e r a l s  formation  (Shik  the corticofugal contribution to the  and c o n t r o l o f v o l u n t a r y  locomotion,  even i n  may be m e d i a t e d v i a t h e p h y l o g e n e t i c a l l y  brainstem  structures  of the extrapyramidal  motor  older  system.  N e u r o a n a t o m i c a l i n v e s t i g a t i o n s have d e m o n s t r a t e d non-mammalian v e r t e b r a t e s birds  al.,  1982  of the  e t a l . , 1 9 6 8 ) . The above  primates,  and  by l e s i o n  In t h e p r e c o l l i c u l a r  by b i l a t e r a l  stimulation  that  i n the midbrain  (MLR)) was n o t b l o c k e d  corticospinal tracts.  However, e l e c t r i c a l  a  t o demonstrate  of a region  of the l a t e r a l  levels  (Yu and E i d e l b e r g ,  (1980) u t i l i z e d  i n d u c e d by s t i m u l a t i o n  o f t h e MLR was u n a f f e c t e d  at midthoracic  of hindlimb walking  precollicular-postmammillary locomotion  the d i s t a l  1968a,b). In t h e c h r o n i c c a t ,  corticospinal tract  recovery  volitional  reduced the animal's  t o p e r f o r m p r e c i s e movements u s i n g  d i d not prevent  pyramidotomy a t t h e  brainstem d i d not i n h i b i t  i n t h e monkey, b u t s e v e r e l y  extremities lesion  198 6) . B i l a t e r a l  that  including fish,  amphibians,  reptiles,  lack direct telencephalo-spinal  projections  (Cabot e t  (bird);  Woodson a n d K u n z l e ,  10  1982  (reptiles,  turtle);  Leonard  et  locomotor intact  al.,  deficits  animals  personal  1979  (fish).  Indeed,  e t al.,  communication).  connections  primates,  minimal  ablation  Grillner,  lateral  funiculus  (for review  and  found t h a t  (LVN)  vestibular  impinge  1984;  few  Jones,  mammals, i n w h i c h  impairment and  in  following  Stuart,  1976;  ( D i e t e r s ' Nucleus)  nucleus  (LVN)  i n the  and  gives r i s e  spinal  cord  Wilson  and  Yoshida,  to  spinal  1968). O r l o v s k y  on  neurons a r i s i n g predominantly  e x t e n s o r motoneurons,  electrical  stimulation  yields  same f a c i l i t a t o r y  the  locomotion  of these  results  or t h e i r  1986)  vestibulospinal  found t h a t  cells  of afferent  i s removed by  peripheral  (^fictive'  p r e p a r a t i o n ) d i d not  (Arshavsky  and and  the  Orlovsky, Yoshida  t e c h n i q u e s t o show t h a t  e t al.  exert  that  rest  (cf. Arshavsky  this  of  ablation  input with paralyzing affect  axons  and  rhythmical a c t i v i t y cerebellar  from  descending  during both  ( O r l o v s k y , 1972a) . A r s h a v s k y  Orlovsky,  Wilson  cells  and  cord  (1972b)  are r h y t h m i c a l l y modulated d u r i n g locomotion, effects  Tectum  ventrolateral  on e x t e n s o r m o t o n e u r o n s i n t h e  vestibulospinal  facilitatory  removal  and  extensive than  see W e t z e l  axons w h i c h t r a v e l  (Pompeiano,  and  exhibit  1975).  descending  t h e LVN  Gabbott  are l e s s  locomotor  L a t e r a l V e s t i b u l a r Nucleus  The  1979;  F u r t h e r , sub-primate  the c o r t i c o s p i n a l  cortical  animals  f o l l o w i n g d e c o r t i c a t i o n when compared t o  (Leonard  exhibit  these  while  agents  rhythmical  activity  198 6 ) . (1968) u s e d  electrophysiological  t h e LVN's s t r o n g e s t l i n k a g e , w h i c h 11  was  monosynaptic,  o c c u r r e d between v e s t i b u l o s p i n a l  e x t e n s o r m o t o n e u r o n s . They f o u n d t h a t f o r m s y n a p s e s on some h i n d l i m b  forelimb  efferents Their  findings  polysynaptic  They were, however, a b l e t o c o n n e c t i o n between  support t h e view t h a t  labyrinthine  righting  reflexes  monosynaptic l i n k  input  on n e c k m u s c u l a t u r e .  excellent  exert  than  the l a t e r a l  They p o s t u l a t e d  i s the  subject  l o c o m o t i o n . Pompeiano  excitatory  influence  both at rest  pathway a n d t h a t extensor  t h e "LVN  n e u r o n s , he p o s t u l a t e d  t h e v e s t i b u l o s p i n a l and  innervating  lateral  ventrolateral investigators, Eidelberg Steeves  of vestibulospinal  n e u r o n s have s y n e r g i s t i c i n f l u e n c e s  hindlimb muscles  funiculus including  e t al.,  input  that  result  t o groups o f motoneurons  (Pompeiano,  vestibulospinal  1984).  tract travels  of the s p i n a l cord. S t e e v e s and J o r d a n  i n the  Several (1980) i n t h e c a t ,  (1981b) i n t h e monkey a n d Sholomenko a n d  (1987) i n t h e b i r d  exerts  motoneurons".  influence  f r o m n e c k and m a c u l a r v e s t i b u l a r  postural  labyrinth reflexes are  Considering the lumbosacral  reticulospinal  i n an  (1984) s u g g e s t e d t h a t  on i p s i l a t e r a l  that  to  v e s t i b u l a r nucleus  adjustments o f hindlimb muscles during m e d i a t e d by t h e v e s t i b u l o s p i n a l  that "the  polysynaptic  p o s i t i o n t o modulate r i g h t i n g r e f l e x e s  during  tonic  labyrinthine  t o neck motoneurons i s l e s s  pathway", t h u s p l a c i n g  The  vestibular  LVN n e u r o n s r e c e i v e  and i n t u r n  d e s c e n d i n g and segmental c o n t r o l  an  motoneurons  and e x t e n s o r m o t o n e u r o n s a t a l l l e v e l s o f t h e c o r d .  afferent  and  fibres  f i n d no m o n o s y n a p t i c l i n k s t o  e x t e n s o r neurons i n c a t s .  demonstrate a strong  vestibulospinal  extensor  (gastrocnemius-soleus) but could  n e u r o n s and n e c k  , found t h a t  lesions  of the  ventrolateral animals,  funiculi  i t appeared  abolished hindlimb  likely  essential  f o r descending  Eidelberg  (1981) f o u n d t h a t  following b i l a t e r a l maintained  cats,  velocities  on  that  a treadmill  control.  locomotor nuclei  although t h e i r was  reduced  in joint  hindlimbs. arising spinal the  extensor drive,  They p o s t u l a t e d t h a t  from  LVN  p l a y an  lesions  Jell  e t al.  stimulation  i n the mesencephalic  deficits  were s t i l l  in either  the  e x t e n s o r EMGs o f t h e  found  only a  particularly  transitory  i n the  i n the  pathways  control  extensors  l e s i o n e d the  able to e l i c i t  of  no  the  during  LVN  l o c o m o t i o n by  c a t . They f o u n d  MLR  major  or t i m i n g of f l e x o r  and  hindlimbs.  Taken t o g e t h e r , t h e above f i n d i n g s LVN-spinal  occur  chronically  the v e s t i b u l o s p i n a l  amplitude  and  compared t o u n l e s i o n e d o r  (1985) a l s o  and  in  was  t o walk a t h i g h e r  adjunctive role  bilaterally  via  However, Yu  c o r d p a t t e r n g e n e r a t o r s which c o n t r o l  step cycle.  pathway  recovery could  ability  sham o p e r a t e d a n i m a l s . F u r t h e r , t h e y reduction  i n these  the v e s t i b u l o s p i n a l  locomotor  vestibular  locomotion  pathway i n t h e c o n t r o l  implicate  of both the  the  descending  righting  m o n o s y n a p t i c c o n n e c t i o n s t o n e c k m o t o n e u r o n s and  reflexes  the  limb  e x t e n s o r p o s t u r a l m u s c l e s v i a a p o l y s y n a p t i c pathway. I t therefore plays  appears  likely  that  i t s most s i g n i f i c a n t  posture during locomotion, basic  locomotor  the v e s t i b u l o s p i n a l  role  i n the c o n t r o l  while having  f i n e tuning locomotion,  behaviours  of balance  l i t t l e effect  on  and the  rhythm.  S i m i l a r t o t h e r o l e p l a y e d by in  projection  i n the  cat  the v e s t i b u l o s p i n a l  the tectum  ( H u e r t a and  appears  pathways  to influence  H a r t i n g , 1 9 8 2 ) . The  motor  tectum  has  been demonstrated t o impinge m o n o s y n a p t i c a l l y formation  n e u r o n s and,  tectospinal  tract.  i n addition, gives  However, t h e  is  cervical  presumably e l i m i n a t i n g a r o l e  control  of hindlimb  CPGs. The  p o s t u l a t e d t o be  movements"  (Huerta  involved  in visual  has  t o my  not,  i n the and  rise  reticular  to  the  tectospinal tract  demonstrated t o descend to only thus  on  spinal  for this  main r o l e  has  cord  levels,  pathway i n  of the  1982),  guidance during  and  the  tectospinal tract  " c o o r d i n a t i o n o f h e a d and  Harting,  been  eye  t h e r e f o r e may  locomotion,  but  the  knowledge, b e e n p o s t u l a t e d t o a f f e c t  be  pathway  the  basic  locomotor p a t t e r n .  Red  Nucleus  The  (Ru)  red nucleus  (Ru)  gives  rise  to crossed  rubrospinal  f i b r e s which f a c i l i t a t e  f l e x o r motoneurons v i a p o l y s y n a p t i c  pathways  1969a,b) d u r i n g t h e  (Hongo et  locomotion  (Orlovsky,  rhythmically electrical this  al.,  1972c). C e l l s  active during  swing  s t i m u l a t i o n of the  phase o f l o c o m o t i o n  (Orlovsky, 1985)  Sarkisyan,  1 9 8 5 ) . As  e l i m i n a t e s the 1972c), w h i l e coincidence  and  Ru  rhythmic  cortical  with  from t h e  the  case  1972c)  and  1 9 7 2 a ) . The  of the  red  , cerebral and  (Fanardzhyan  and  cerebellar ablation  activity  during  locomotion  a b l a t i o n has  little  effect  locomotor swing phase  during  nucleus  (Fanardzhyan  LVN,  of  activity  cerebellum  d o r s a l column n u c l e i i n the  are  enhances f l e x o r  1972c), b a s a l g a n g l i a  Sarkisyan,  nucleus  (Orlovsky,  (Orlovsky,  r e c e i v e s major a f f e r e n t i n p u t s cortex  Ru  i n the  swing phase  (Orlovsky,  on i t s  (Orlovsky,  1972c).  However, b i l a t e r a l tracts al.,  ( S t e e v e s and  1968/  little  Jordan,1980/  effect  Steeves, on  s t u d i e d . While  the  the  1932/  and  parts  appears  (1985) e n v i s a g e t h e integration initiated "fine  control  origin role  but  movement o f and  to  distal  Sarkisyan  motor/sensory  correction  that  i s not  importance  of  an  the red nucleus  essential  acts  i n the  rhythm.  Formation  and  i n the  hindbrain reticular reticulospinal  control  formation neurons are  pathway w h i c h p l a y s an  of locomotion  (Lawrence and  e t a l . , 1981b/ E i d e l b e r g ,  1980/  Afelt,  1987/  Orlovsky,  Kuypers,  Jordan,  then,  animal  needs,  important  movement. I t a p p e a r s ,  has  of r e s o l u t i o n  red nucleus  c e n t r e f o r t h e m o n i t o r i n g and  of the  Eidelberg  independent  et  (1982) p o s t u l a t e d  level  locomotor  as an  1968b)  t o have l i t t l e  Fanardzhyan  o f t h e b a s i c motor  Mid-  Kuypers,  Kuypers  Shik  1985/  limbs. S i m i l a r l y ,  t u n e " motor c o n t r o l ,  Reticular  basic  with respect to the  of i n d i v i d u a l  e t al.,  1981/  c h r o n i c or acute  adds a s e c o n d  s t r u c t u r e s which subserve  or r u b r o s p i n a l  Eidelberg,  Jell  i n any  red nucleus  rubrospinal tract  particularly  and  Yu  1987b/ Lawrence and  locomotion  the  red nuclei  the b a s i c p a t t e r n s of locomotion,  that  to  of the  Ingram and Ranson,  Sholomenko and  for  ablation  1980/  1974/  Steeves  e t al.,  1987/  important  Kuypers,  Steeves  and  Afelt,  1974/  Steeves,  1968b/  Jordan,  Sholomenko and  1 9 7 0 a , b ) . L e s i o n s t u d i e s i n t h e monkey  1968b/ E i d e l b e r g  (Sholomenko and  1981/  the  Steeves, (Lawrence  e t al.,  1981b),  cat  (Steeves  Eidelberg,  1981b),  and  bird  1987b) d e m o n s t r a t e  that  and  interruption  of  the  reticulospinal  severely  impairs  intracellular a majority  pathway o r a b l a t i o n o f i t s c e l l s  locomotor a b i l i t y .  r e c o r d i n g i n the  of r e t i c u l a r  modulated d u r i n g : preparation,  2)  1)  acute  formation  e s t a b l i s h e d the  and  3)  subthalamic  regions  of d i r e c t  reticular  stimulated  (MLR  elicited  locomotion  activation  i n the  stimulation  1986;  (Mori  of the  e t a l . , 1978;  Noga e t al.,  (Steeves  reticular  may  e t al.,  formation  rat  findings.  has  into  by  neurons.  send c o l l a t e r a l s  shows t h a t  to  electrical  locomotion  Skinner,  1987b;  1988)  and  agonists  and  new  approach of  injecting  in  the  Jordan, bird  two  and  extended  types  antagonists  eliciting  neurotransmitter  electrophysiological!^  corroborated  This approach y i e l d s  neurotransmitter  pyramidal  monosynaptically  elicits  and  comparatively  antagonists  locomotor regions  to a  that  some d e g r e e o f motor  ( K i n j o e t al.,  or b l o c k i n g locomotor behaviour and  reticular  1986).  Studies using the  agonists  region  also  and  formation  exert  Garcia-Rill  1988),  the  precollicular  mediated  of r e t i c u l a r  n e u r o n s and  in  locomotor  o r SLR)  neurons, t h e r e f o r e , presumably  formation  that  thalamic  (1970a) f o u n d  c o n t r o l v i a t h i s pathway. R e c e n t e v i d e n c e  cat  i n the  s t i m u l a t i o n of the pyramids r o s t r a l  Corticofugal  found  e x c i t a t o r y monosynaptic  neurons. In a d d i t i o n , O r l o v s k y  antidromic  cat,  p r e p a r a t i o n . He  p o s t m a m m i l l a r y p r e p a r a t i o n t h a t was via  using  n e u r o n s were r h y t h m i c a l l y  thalamic  existence  l i n k s between t h e  transection  origin  M L R - e l e c t r i c a l l y stimulated locomotion  (SLR)-stimulation i n the  electrical  (1970b),  decerebrate  spontaneous locomotion  mesencephalic preparation  formation  Orlovsky  of  identified  previous  of information.  First,  are thought to act  at  receptors bodies,  (Goodchild  dendrites  e t al.,  and  1982). R e c e p t o r s are  t e r m i n a l s but  axons i n a p p r e c i a b l e numbers activity  e v o k e d by  would l i k e l y due  to the  electrical these  be  direct  due  have n o t  (Goodchild  to the  activation  neurochemical  of these  "locomotor"  characterization identification  affecting  Second, t h e  of receptor types,  of neurons i n v o l v e d i n the  i n t o the  reticular  be  a c t i v a t e d by  1985;  al.,  e t al.,  1988;  1985;  Sholomenko and  1987a; Noga e t al., e t al.,  combination  neurochemical  descending  1988)  et  al.,  antagonists 1987a; Noga  (glutamate,  Sholomenko  Substance P  from l e s i o n ,  n e u r o n s as b e i n g  the  y e t t o be  origin  spinal  However, t h e n e u r o t r a n s m i t t e r ( s ) has  injected  and  (Noga e t a l . ,  stimulation  and  studies strongly implicate  pathway c o n t r o l l i n g  pathway i t s e l f  1985;  and  process.  1986).  of r e s u l t s  injection  reticulospinal  e t al.,  of  locomotion  Steeves,  agonists  an  the  (Garcia-Rill  1987a), G A B A e r g i c  (Garcia-Rill  Garcia-Rill The  Steeves,  not  the  agents  demonstrated t h a t  1988), e x c i t a t o r y amino a c i d  a s p a r t a t e , NMDA) Steeves,  has  cholinergic agonists  Sholomenko and  (Garcia-Rill et  formation  injection  locomotor  stimulation with various neuroactive  and  traverse  aiding in  Chemical  can  receptors  leads to  thereby  to  infusion  selective  neurochemicals  cell  1 9 8 2 ) . Thus,  s t i m u l a t i o n o f axons o f p a s s a g e w h i c h may stimulation site.  on  been l o c a l i z e d  e t al.,  intracerebral  found  major  cord rhythmic  utilized  determined  17  of the  by  the  (Jordan,  oscillators.  reticulospinal 1986).  Locomotor Regions and  Higher order  brainstem  Locomotion-Related  structures  that  have d i r e c t d e s c e n d i n g c o n n e c t i o n s t o t h e generators  brainstem n u c l e i that  s p i n a l pathways d e s c r i b e d have e a s i l y  identifiable  v i r t u e of the  regions still  can  neuroanatomical  actions  the  ganglia  are  as b e i n g  electrical  (PLS),  s u c h as also  exact  l o c a t i o n and  observed with  subthalamic  structures  spinal cord  rise  as  the  (SLR) the  stimulation  direct  and  in  of  have  these  controversy  hodological  locomotor region. the  implicated  not  locomotion  stimulation  of the  do  substrates  pontobulbar  mesencephalic locomotor region  cerebellum,  strongly  d r i v i n g and/or  substrates involved  not  locomotor  to the  p r o d u c e l o c o m o t o r a l t e r a t i o n s . Thus,  locomotor s t r i p and  finding that  e x i s t s over the  f o r the  give  do  a b o v e . Some o f t h e s e s t r u c t u r e s  been p h y s i o l o g i c a l l y i d e n t i f i e d by  apparently  o r m o t o n e u r o n s have b e e n i m p l i c a t e d  modulating the  Structures  (MLR)  Other higher  order  l i m b i c s y s t e m and  basal  i n motor c o n t r o l .  Cerebellum  The direct and  cerebellum  and  indirect  from a l l o f the  has  the  remarkable a t t r i b u t e of  information CNS  1986). A f t e r p r o c e s s i n g  f r o m most p e r i p h e r a l  motor c e n t r e s the  data,  ( A r s h a v s k y and  i t returns  information  back t o  supposition  comes f r o m A r s h a v s k y ' s g r o u p who  dorsal tract  a l l of the  spinocerebellar tract (VSCT) and  receiving  the  motor c e n t r e s .  (DSCT), v e n t r a l  Orlovsky,  integrated  Support  for  this  have f o u n d t h a t spinocerebellar  spinoreticulocerebellar tract  18  receptors  (SRCT) r e l a y  the  different  t y p e s o f i n f o r m a t i o n t o t h e c e r e b e l l u m ( f o r r e v i e w see  Arshavsky  and O r l o v s k y , 198 6 ) . The DSCT r e l a y s  information  c o n c e r n i n g a c t u a l movements f r o m t h e p e r i p h e r a l m o t o r s y s t e m and is  silent  i n t h e absence  VSCT and SRCT t r a n s m i t t h e c e r e b e l l u m even  o f muscle  centrally  contractions,  generated neural  i n t h e absence  o f rhythmic  feedback  s u c h as i s f o u n d i n a f i c t i v e  Further,  Arshavsky's experiments  t h e s e pathways c a r r y oscillator  elements  s p i n a l motoneurons cerebellum  also  I t s major nuclei,  information colliculus,  t h e head  and  neurons  the state  sensory system v i a t h e  give r i s e  The r e t i c u l a r  a l l appear  activity  1970a,b; 1 9 7 2 a , c ) .  formation  t o the output  formation, red nucleus  t o be r h y t h m i c a l l y  o f neurons  In a d d i t i o n ,  the cortex v i a the w e l l and O r l o v s k y  The  of equilibrium v i a  f r o m t h e c e r e b e l l u m , i n whose a b s e n c e ,  spontaneous  s u c h as  concerning the v i s u a l  and neck  r e d n u c l e u s a n d LVN w h i c h  output  rhythmic  outputs include the r e t i c u l a r  pathways d i s c u s s e d above.  by  from c e n t r a l  and from t h e c o r t e x v i a t h e p o n t i n e n u c l e i .  hindbrain  and v e s t i b u l a r  (paralyzed) preparation.  ( A r s h a v s k y and O r l o v s k y , 1 9 8 6 ) .  system,  system  peripheral  r a t h e r t h a n from output elements  system v i a t h e s u p e r i o r  trigeminal  information to  support the hypothesis that  information  receives  the v e s t i b u l a r  while both the  modulated  the rhythmicity  was r e d u c e d ( O r l o v s k y ,  the cerebellum also  influences  characterized thalamic loop.  Arshavsky  (198 6) d e s c r i b e t h e c e r e b e l l u m as an o r g a n  can o r g a n i z e t h e i n t e r a c t i o n  of a variety  which  of locomotor  3 synergisms  . Thus,  i t can monitor  i n f o r m a t i o n b o t h from t h e  3 "Bernstein movements. determine spatial  proposed  the hypothesis  o f the m u l t i - l e v e l  According to h i s hypothesis higher the chains  coordinates.  o f motor Still  activity,  lower  levels  sections  t h e lower solve  level  t h e motor  system  of control  o f t h e nervous ties  movements t o  problem  as  of  system  such  by  environment "select  and t h e c u r r e n t s t a t e  essential  transmission another"  (Arshavsky  locomotor prevent: 2)  d a t a " from t h i s  of signals  Although  from  and  one  spontaneous  locomotion  by  preparation  evoked  1972a,b,c).  The  variety  by  can a f f e c t  stimulation  o f course, negate  i n the c o n t r o l  Pontobulbar  The  stimulation  indicate that  of the  the  mesencephalic  while  cerebellar  output v i a a  ( S h i k and  importance  of the  i n the  strip  (PLS)  electrical  was  (for review, organizing  the  operatively "the  1977;  Mori  1986)  necessary mechanisms may  and  stimulation  e t al.,  t o a wide r a n g e  see M c C l e l l a n , 1986).  controlling  neuronal  1987)  be  interaction this  work."  animal.  physiologically  of  elements  ( c f . Shik  The  controlling  a  given  d e s c r i b e d as  a  locomotor  al.,  motor  1977).  20  act"  to  ranges  joints,  1966).  At  (Arshavsky  synergism.  this  More r e c e n t birds  of vertebrate species  strip  (muscles,  et  of  postmammillary  s t u d i e s have g e n e r a l i z e d t h e e x i s t e n c e o f t h e PLS ( S t e e v e s e t al.,  cerebellum  intact  i n the p r e c o l l i c u l a r  Yagodnitsyn,  for  (PLS)  locomotor  locomotion  in  r h y t h m . T h i s s u p p o s i t i o n does  motor a c t i v i t y  finding that  region e l i c i t e d  Orlovsky,  SLR  ( O r l o v s k y , 1970a,b;  of locomotor  the obvious  Locomotor S t r i p  pontobulbar  d e f i n e d by  cat  i n the thalamic preparation,  o f t h e MLR  locomotor  of ongoing  to  not  o f output pathways, t h e c e r e b e l l u m i s not e s s e n t i a l  the genesis of the b a s i c not,  i n t h e c a t does  locomotion i n the  the q u a l i t y  system  to play a strong role i n  electrical  above r e s u l t s  " r e g u l a t e the  1986).  locomotion  initiated  synergism,  of the nervous  ablation  t h e t h a l a m i c p r e p a r a t i o n o r , 3)  efferents  part  Orlovsky,  cerebellar  locomotor  i n f o r m a t i o n , and  the c e r e b e l l u m appears  control, 1)  of each  limbs) each and  along the and level,  extent  of the descending  nerve  and n u c l e u s o f t h e t r i g e m i n a l  ( M o r i e t al., 1977; S h i k a n d Y a g o d n i t s y n ,  rostrocaudally nucleus and  tract  from t h e l e v e l  of the trigeminal  (MesV) t o t h e c a u d a l m e d u l l a  Yagodnitsyn,  region proposed  1977, 1 9 7 8 ) . by G a r c i a - R i l l  (1986) p o s t u l a t e d t h a t  Although  n o t i n agreement w i t h t h e  e t al. (1986,  (Jordan,  1986).  and S k i n n e r  A recent review,  tracing  retrograde tracers  neurons  locomotor  (Garcia-Rill  nucleus  s t u d i e s which demonstrate  ventromedial  reticular  injected  1986),  (PPN) as t h e  s u g g e s t i o n comes  i n t o t h e PLS l a b e l  tracers  (mMLR)  neurons  e t al.,  that  predominantly  a n d o n l y s m a l l numbers o f PPN n e u r o n s ,  neuroanatomical  region  i n t e r n e u r o n s t o more c a u d a l PLS  m e d i a l MLR. E v i d e n c e t o s u p p o r t s t h i s  of  Jordan  (1986) a n d i s t h o u g h t t o  however, d e s i g n a t e s t h e p e d u n c u l o p o n t i n e  neuroanatomical  1987),  t h e r o s t r a l h e a d o f t h e PLS (MesV) i s  d e f i n e d by G a r c i a - R i l l intranuclear  mesencephalic  ( M o r i e t al., 1977; S h i k  synonymous w i t h t h e m e d i a l m e s e n c e p h a l i c  project  1977, 1978)  while  i n t o t h e mMLR l a b e l  formation structures  from injection MesV  anterograde mainly  (Garcia-Rill  et a l . ,  1983b) . The appears  name PLS may be a misnomer b e c a u s e t o extend  funiculus  c o n t i n u o u s l y caudalward  (DLF) o f t h e s p i n a l  1983a,b; Dubner a n d B e n n e t t 1986).  Kazennikov  (Kazennikov  see M e C l e l l a n ,  t h e PLS may be a p o l y s y n a p t i c  e t a l . , 1983a,b) whose c e l l s  Garcia-Rill  e t al., 1980,  e t al., 1977; S h i k a n d Y a g o d n i t s y n ,  ventromedial t o i t s descending 1984).  also  into the dorsolateral  1983; f o r r e v i e w  I t has been p o s t u l a t e d t h a t  p r o p r i o s p i n a l pathway.(Mori 1978;  cord  the s t r i p  fiber tract  of origin l i e  ( S e l i o n o v and Shik,  (1983) o r i g i n a l l y d e s c r i b e d t h e PLS as b e i n g  coextensive with Probst's tract coursing  just  (Garcia-Rill  ventral  1983b). J o r d a n argue  t o the nucleus  and Skinner,  the mesencephalic  formation and descending (Noga e t al., 1988), trigeminal  Jordan,  observations reticular  (Shefchyk  cells  reticular  including:  1) c o o l i n g  1988)  reticular  formation  o f the  o f t h e MesV/mMLR r e v e r s i b l y This finding  between t h e PLS a n d r e t i c u l a r  t h e PLS  ( S t e e v e s and,  ipsilateral  t h e PLS a b o l i s h e s l o c o m o t i o n p r o d u c e d e t al., 1 9 8 4 ) .  a b o l i s h e d by t r a n s e c t i o n  blocks  locomotion  suggests  a blockade  formation t o spinal  of the cord  i naddition to  formation t o spinal  pathway between t h e mMLR a n d r e t i c u l a r  medial  by e l e c t r i c a l  formation linkage,  a b l o c k o f t h e mMLR t o r e t i c u l a r  cord  f o r m a t i o n . 2) c o o l i n g o f b y mMLR  stimulation  3) PLS s t i m u l a t e d l o c o m o t i o n i s n o t o f the p r o p r i o s p i n a l  PLS-DLF pathway a t  (Noga e t a l . , 1988) a n d 4) e x t e r o c e p t i v e s t i m u l a t i o n o f  the t r i g e m i n a l afferents afferent  receptive  [e.g. p i n n a (FRA)  locomotion Both  Noga e t al.,  ( M a t s u s h i t a e t al., 1981,1982)  pathway f r o m mMLR t o PLS t o r e t i c u l a r  C2-C3  from  T h i s h y p o t h e s i s i s s u p p o r t e d by s e v e r a l  et al., 1 9 8 4 ) .  (Shefchyk  t o CI  e t al.,  nucleus c o n s t i t u t e  f o r m a t i o n d u r i n g locomotion evoked  stimulation  medulla  a n d have a d u a l o u t p u t b o t h t o downstream  i nthe medial  1984).  fibers  afferents  (Garcia-Rill  i nthe l a t e r a l  trigeminal  nuclear  rostral  ( J o r d a n , 1986;  bodies  (propriospinal)  and t o n u c l e i  nucleus  and co-workers cell  from  1986) ) w h i c h r e c e i v e s  trigeminal  strongly that  (i.e. trigeminal  Jordan  field  (Aoki and M o r i ,  stimulation,  (for review  and a v a r i e t y  1981) a n d f l e x o r  (Jankowska e t a l . , 1967)]  see Jordan,  and co-workers  o f other  1986;  ( J o r d a n , 1986;  sensory reflex evokes  Noga e t al., 1988). Noga e t al., 1988)  and  Garcia-Rill elicited results  and S k i n n e r  by s t i m u l a t i o n from  afferent  (198 6) now s u g g e s t  o f t h e PLS-DLF s y s t e m  trigeminal  This places the descending  modulated to  input to t h i s  trigeminal  p o s i t i o n very s i m i l a r t o that i n which a f f e r e n t  that  the locomotion  mimics t h a t  which  locomotor  region.  n u c l e a r complex  of the l a t e r a l  in a  vestibular  nucleus  i n p u t f r o m t h e p e r i p h e r y , w h i c h may be  by comparator  s y s t e m s s u c h as t h e c e r e b e l l u m ,  i s able  a l t e r motor output b u t i s n o t r e s p o n s i b l e f o r t h e p r i m a r y  locomotor  rhythm.  Recent elicit  studies u t i l i z i n g  locomotion suggest  stimulation-induced control  eliciting  field  i s under GABAergic  1988). Noga e t al.(1988)  l o c o m o t i o n c o u l d be e l i c i t e d antagonist picrotoxin  stimulation to  that PLS/trigeminal  locomotion  (Noga e t a l . ,  trigeminal  neurochemical  by i n j e c t i o n  i n c l u d i n g glutamate  and Substance  that  following neurochemicals,  P, a l s o p r o d u c e d  i n t o t h e PLS  (Noga e t a l . ,  However, t h e a n a t o m i c a l s u b s t r a t e s t h r o u g h w h i c h neurotransmitters affect  found  w h i c h a l o n e was i n e f f e c t i v e a t  i n t o t h e PLS. O t h e r  b e h a v i o u r when i n j e c t e d  that  GABAergic  i n t o t h e PLS. F u r t h e r , t h e y  stimulation,  injection  found  of the  l o c o m o t i o n , w o u l d evoke l o c o m o t i o n  picrotoxin  inhibitory  locomotor  control  locomotor 1988).  these  have y e t t o be  determined.  Mesencephalic  The when t h e y  Locomotor Region  classical  (MLR)  MLR was c h a r a c t e r i z e d by S h i k e t a l . (1966)  found t h a t  focal  high frequency e l e c t r i c a l  stimulation  of a region l a t e r  identified  cuneiform nucleus  ( S h i k e t al.,  mesencephalic the  force  preparation Later  f o r the  investigators  rat  relations  (Mogenson e t al.,  o f t h e MLR  (Eidelberg  1985;  Steeves,  anterograde  to the  Steeves  stated,  Steeves  and  (heavy p r o j e c t i o n )  p o n t i n e and m e d u l l a r y  tegmental nigra  inferior field,  colliculus, ipsilateral  (Garcia-Rill  Jordan, and  (1984),  techniques  using  from  the  (light  fields  central substantia of Forel  intralaminar nuclei,  zona  lateral  hypothalamic  neuroanatomical  tracing  subthalamic  nucleus. Electrophysiological techniques demonstrated  and  levels,  i n n u c l e i which i n c l u d e d the t h a l a m i c  and  also  cuneiform  t e r m i n a l s were f o u n d  medial  & MLR  f o r m a t i o n . They  (VTA). A t d i e n c e p h a l i c  incerta,  in  that  3  p e r i a q u e d u c t a l gray,  area of Tsai  Steeves,  contralateral  reticular  reticulata),  bird  ([ H]proline  projections and  1984),  (1970a) f o u n d  superior colliculus,  ( b o t h p a r s compacta and  v e n t r a l tegmental  animals  1986)  f o u n d a s c e n d i n g p r o j e c t i o n s t o t h e more r o s t r a l nucleus,  of  and  descending  Jordan  descending  this  location  cat  and  Orlovsky  connections with  demonstrated  ipsilateral  projection)  1983;  of  mechanisms.  the  e t a l . , 1981),  in a  of  t h e r e b y making  in a variety  autoradiographic tracing  [ H]leucine), 3  neurons.  frequency  to c l a r i f y  the  variation  i n p r e p a r a t i o n ; W e b s t e r and  had monosynaptic  reticulospinal  found t h a t  Mogenson and Wu,  p r e p a r a t i o n ) . As p r e v i o u s l y t h e MLR  locomotion  s t u d y o f motor c o n t r o l  a l . , 1983a,b; G a r c i a - R i l l ,  (Sholomenko and  gait,  have a t t e m p t e d  i n c l u d i n g t h e monkey et  evoked  c o u l d modulate the  o f s t e p p i n g and  ideal  input/output  1967)  i n close proximity to  c a t p r e p a r a t i o n . They a l s o  stimulus parameters  stepping,  as l y i n g  nucleus and  afferent  p r o j e c t i o n s to the substantia nigra, of the ansa  f e l i n e MLR  from the p a r s r e t i c u l a t a  entopeduncular nucleus, c e n t r a l  lenticularis,  m e d i a l and  c e n t r a l n u c l e u s o f t h e amygdala Garcia-Rill, tritiated slightly  different  (1984). W h i l e ipsilateral formation,  labelling  laterality  i n j e c t i o n by al.  group  was  recently  r e p o r t e d by  tract  (Garcia-Rill  group.  result  and  and  Jordan  Skinner  such t h a t  nucleus which  descending t r i g e m i n a l 1986).  reticular  from t h e  anatomical  monosynaptic  n u c l e a r complex  Garcia-Rill  two  Thus, t h e c l a s s i c a l  divisions MLR  et  tract  ( 1 9 8 4 ) . More  (1986,  1987b) MLR-Probst's  trigeminal  (Garcia-Rill  that  exerts control  connection with the  Recently,  of the  i s known t o s e n d p r o j e c t i o n s t o t h e  i t seems l i k e l y  substrate,  found  in projection  and  (1970a) t h a t  connections with spinal p r o j e c t i n g  formation neurons,  of  formation  the apparent  Combined w i t h O r l o v s k y ' s f i n d i n g  have m o n o s y n a p t i c  1983b)  f r o m t h e mMLR t o P r o b s t ' s  projection probably arises  mesencephalic  Jordan  reticular  e t al.,  In a d d i t i o n ,  Steeves  however, G a r c i a - R i l l  reinterpreted this  and  gave  a t t r i b u t e d t o a more m e d i a l p l a c e m e n t  Garcia-Rill's  not  1983a,b;  t h e MLR  However, d i f f e r e n c e s  (1983b) f o u n d a p r o j e c t i o n  which  and  (1984) f o u n d a p r e d o m i n a n c e  of c o n t r a l a t e r a l  injection.  nucleus  studies u s i n g the  i n t h e p o n t i n e and m e d u l l a r y  Garcia-Rill's  c o u l d be  e t al.,  than those of Steeves Jordan  gray,  hypothalamus  into  3  S t e e v e s and  after  transport  [ H]leucine injected  results  a higher proportion labelling  (Garcia-Rill  1983). A n t e r o g r a d e  amino a c i d  lateral  of the  MLR  neurons  reticular  whatever i t s  o v e r motor f u n c t i o n v i a i t s  reticular-formation.  o f t h e MLR  d e s c r i b e d by  25  t h e MLR,  Skinner,  have b e e n  S h i k e t al.,  postulated. (1966)  [now  called and  the l a t e r a l  a MLR  MLR  (1MLR) J o r d a n ,  (PPN/MLR) l o c a t e d w i t h i n t h e c o n f i n e s o f t h e  pedunculopontine  tegmental  nucleus  have b e e n d e s c r i b e d . S u p p o r t also  comes from  studies  o f t h e PPN e v o k e d (Garcia-Rill  i n t h e r a t , where e l e c t r i c a l  locomotion  and Skinner,  i n the decerebrate  Brudzynski  e t al., 1988).  Brudzynski  e t a l . (1988)  (Mogenson et al., 1985;  As w i l l  be d i s c u s s e d more f u l l y  a l s o d e s c r i b e d more l a t e r a l  s t i m u l a t i o n b u t w h i c h show d i f f e r e n t  with respect t o chemical  i n reviewing  c o n n e c t i o n s t o t h e r a t PPN, l i s t e d subpallidal  area  sites,  preoptic  a r e a ) , t h e zona  hypothalamus/preoptic  t h e n u c l e u s accumbens, t h e  incerta,  i n n o m i n a t a and the medial  that  t h e accumbens,  control  In an a t t e m p t  locomotor  of the mesencephalic  a variety  behaviour.  o f neurochemicals  c a t . They f o u n d t h a t  antagonists picrotoxin  a n d zona  i n limbic  t o evoke o r b l o c k l o c o m o t i o n ,  (1985) i n j e c t e d  GABAergic  over  connections t o  subpallidal  i n c e r t a p r o j e c t i o n s t o PPN may p l a y a r o l e ("motivational")  preoptic  and t h e a n t e r i o r  a r e a as a l l s e n d i n g d i r e c t  t h e PPN. They p r o p o s e d  characteristics  neuroanatomical  (including the substantia  the subthalamic nucleus  elicited  below,  stimulation.  Mogenson e t al. (1985),  al.  animal  e q u i v a l e n t t o t h e PPN/MLR, w h i c h evoke l o c o m o t i o n upon  electrical  area,  stimulation  1986) a n d i n c r e a s e d motor a c t i v i t y i n  f r e e l y moving a n i m a l  lateral  (PPN) ( G a r c i a - R i l l , 1986)  f o r t h e e x i s t e n c e o f t h e PPN/MLR  the i n t a c t  possibly  1986; Noga e t a l . , 1988]  G a r c i a - R i l l et i n t o t h e PPN/MLR  injection  and b i c u c u l l i n e  of the  i n t o t h e mMLR  l o c o m o t i o n w h i c h c o u l d be b l o c k e d by t h e i n f u s i o n o f  GABA o r m u s c i m o l a t t h e same l o c a t i o n .  Further, they  found  that  glutamate  (at h i g h c o n c e n t r a t i o n ) r e d u c e d  threshold  and  a c e t y l c h o l i n e was  ineffective  l o c o m o t i o n . A l s o , s t u d i e s from t h i s 1985;  Garcia-Rill  injection cat. and  In t h e  intact  glutamate  cholinergic al.,  Skinner,  ( B r u d z y n s k i et  glutamate  t o be  al.,  1988)  be  was  elucidated,  but  given. F i r s t ,  and  stimulation,  recruitment  instantaneous with the  of glutamate  through  t o evoke l o c o m o t i o n rapidly  and w i t h  rat  than  PPN  the mesencephalic major r o l e  the t i s s u e  i s both  natural  to a s u f f i c i e n t  dependent  the  diffusion  number o f  e t al.  (1985)  utilized  the  an  was  modulating  used  plays a  et  al., intact  already  introduction  accumbens. I t i s l i k e l y  with high baseline activation,  o f a s m a l l number o f l o c o m o t o r  compact  level  level  cells  o c c u r more  s m a l l e r more  1988)  and  and  intensity  of stimulation,  (1986,  the  r a t than  or m e t a b o l i z e d  made e v e n h i g h e r by  o f amphetamine i n t o t h e n u c l e u s animal  t a k e n up  of  possible  is a  i n which the a c t i v a t i o n  i n some c a s e s was  intact  several  o f l o c o m o t i o n , (see M o r i  e t al.  i n the  (Brudzynski  i n the  p r e p a r a t i o n i n which a c t i v a t i o n  f r e e l y moving animal  the  motor a c t i v i t y  c a t . Second, G a r c i a - R i l l  i n the e l i c i t a t i o n  P  picrotoxin  while i n j e c t i o n  degradation i n the  1982), w h i l e B r u d z y n s k i  h i g h and  of  o r change t h r e s h o l d w o u l d l i k e l y  less  i n the  Substance  where c u r r e n t s p r e a d  onset  al.,  i n t o t h e PPN/MLR  glutamate  (activation)  et  locomotion  more e f f e c t i v e  n e u r o t r a n s m i t t e r which i s r a p i d l y unlike e l e c t r i c a l  eliciting  (Garcia-Rill  long l a s t i n g  agonist carbachol reduced  e x p l a n a t i o n s may  in  showed t h a t  i n c r e a s e d motor a c t i v i t y ,  the c a t remains  electrical  f r e e l y moving r a t , i n j e c t i o n  1 9 8 8 ) . Why  therefore  group  1986)  i n t o t h e mMLR e l i c i t e d  significantly  et  and  the  the  that  in  recruitment  neurons w i l l  cause  a  significant  i n c r e a s e i n locomotor  mesencephalic  activity,  preparation, the activation  increased  from a lower b a s e l i n e b e f o r e  elicited.  Brudzynski  the  cholinergic  locomotion,  agonist carbachol  by t h e c u n e i f o r m  p o s s i b l y coextensive  injection  may r e f l e c t  i n t o t h e same s i t e .  effect  reduced  injections  e t al.  c o u l d be r e v e r s e d by  e t al.  2)  a c e t y l c h o l i n e instead of the longer a c t i n g  e t al., 1 9 8 8 ;  nucleus, Fibiger  ( V i n c e n t e t al., 1983)  s u b s t a n t i a innominata  and l a t e r a l  intrinsic  (Goldsmith reticulata,  a n d Semba,  1988),  4)  send 1988)  p r o j e c t i o n s t o t h e PPN,  (Brudzynski  c h o l i n e r g i c neurons p r e s e n t  and Van d e r Kooy,  on t h e MLRs  w h i c h may  p r e o p t i c area,  s e n d c h o l i n e r g i c p r o j e c t i o n s t o t h e PPN 3)  experimental  o f pathways i m p i n g i n g  l a t e r o d o r s a l tegmental  (Brudzynski  Substance P  1988),  discrepancy  (Taylor, 1985a,b).  i n c l u d e t h e : 1)  and  no  however, t h e u s e o f t h e s h o r t e r a c t i n g ,  Putative nuclear origins  cholinergic  found  i n t o t h e PPN/MLR o f t h e  c a r b a c h o l may be r e s p o n s i b l e f o r some o f t h e s e differences  distribution  (1985)  c a t p r e p a r a t i o n . Reasons f o r t h i s  quickly metabolized  effects  f r o m t h e two MLRs. U n l i k e  (1988), G a r c i a - R i l l  r e m a i n t o be d e t e r m i n e d ,  locomotion  These d i f f e r e n t  when a c e t y l c h o l i n e was i n j e c t e d  mesencephalic  into the  PPN a n d p e r i a q u e d u c t a l  the previously discussed d i f f e r e n t i a l  o f r e c e p t o r s and/or p r o j e c t i n g f i b r e s Brudzynski  that injections of  i n t o t h e PPN  Both e f f e c t s  be  c a n be  w i t h t h e 1MLR, i n c r e a s e d  i n t h e f r e e l y moving a n i m a l . atropine  a l s o found  nucleus,  i nthe  l e v e l must f i r s t  locomotion  w h i l e more d o r s a l and l a t e r a l  region bordered gray,  (1988)  e t al.  while  w h i c h may e t al.,  i n t h e PPN  Substantia nigra,  pars  w h i c h a p p e a r s t o s e n d a G A B A e r g i c i n p u t t o PPN  28  (Garcia-Rill w h i c h sends  and  Skinner,  i n p u t t o PPN  1986),  5)  entopeduncular  (Garcia-Rill  Nucleus  accumbens, w h i c h s e n d s  nucleus  (Garcia-Rill  and  and  Skinner,  i n p u t t o t h e PPN  Skinner,  1986).  nucleus, 198 6) and  and  cuneiform  Other p r o j e c t i o n s  t h e MLRs have b e e n d e s c r i b e d above, b u t t h e t y p e  6)  to  of  n e u r o t r a n s m i t t e r s e m p l o y e d i n t h e s e pathways r e m a i n s  to  be  elucidated.  Subthalamic  The  Nucleus  and  Subthalamic  subthalamic nucleus  the p o s t e r i o r involved  and  lateral  While  s u b t h a l a m u s i n an o t h e r w i s e  of the  intact  1979).  and  alternating  F l y n n , 1968),  H a e r t i g and Masserman, hypothalamic  cat  1940), et  (Eidelberg  the subthalamic  electrical  of the  prevent  unilateral  destruction  i n humans  stimulation  anaesthetized (Waller,  thalamic al.,  ( O r l o v s k y , 1969b),  1985),  e t al.,  as w e l l  intact 1940; and  as i n t h e  r e g i o n as b e i n g i m p o r t a n t  of the neuraxis r o s t r a l  of  1981b). F u r t h e r e v i d e n c e  l o c o m o t i o n comes f r o m t h e o b s e r v a t i o n t h a t transection  be  s t e p p i n g movements i n t h e  lightly  (Eldridge  d e c e r e b r a t e monkey implicating  In a d d i t i o n ,  to  destruction  c a t does n o t 1940),  (including  appear  subthalamic nucleus underlies hemiballismus  region e l i c i t s  (Siegel  also  bilateral  ( H a e r t i g and Masserman,  (Hammond e t al., this  Region  subthalamic region  hypothalamus)  i n motor c o n t r o l .  locomotion  and  Locomotor  to  animals with a  to the subthalamic  nucleus  (a p r e c o l l i c u l a r - p r e m a m m i l l a r y d e c e r e b r a t i o n ) w i l l  spontaneously  locomote,  (a  while a transection  precollicular-postmammillary  removing  this  nucleus  decerebration) eliminates  spontaneous a c t i v i t y Skinner,  ( S h i k e t al., 1967; G a r c i a - R i l l and  1986). O r l o v s k y  subthalamic  locomotor  (1969) f o u n d t h a t  region  not w i t h i n , t h e subthalamic in  a site  nucleus  dorsomedial  to,  evokes t r e a d m i l l  o f t h e MLR d i d n o t i n t e r r u p t  d i d reduce  the bouts  o f spontaneous locomotor  decerebrate cats with b i l a t e r a l  1966; S i r o t a  efferents  and Shik,  (ZI) and l a t e r a l  l a b e l l e d with the anterograde  transection  area  (LHA) w h i c h were  locomoting precollicular-premammillary  a n d may be damaged w i t h t h e t y p e  afferent  projections  of cerebrovascular A l s o , t h e ZI  from t h e c o r t e x ,  f o r m a t i o n and s u p e r i o r c o l l i c u l u s ,  e f f e r e n t s t o t h e PPN a n d b a s a l g a n g l i a  mesencephalic  while  i n a position  Recently,  system  to integrate a n d MLR  E l d r i d g e e t al.  demonstrated  that  i n f o r m a t i o n between t h e b a s a l  (Mogenson and Wu,  198 6 ) . (1988) have  o f t h e GABAergic a n t a g o n i s t  30  1986).  strategically  (1985) and W a l d r o p e t al,  injection  sending  (Mogenson and Wu,  Mogenson a n d Wu d e s c r i b e t h e ZI r e g i o n a s b e i n g  limbic  The  n u c l e u s , w o u l d be s p a r e d i n  receives  ganglia,  injection  (Mogenson e t al.,1985).  a s s o c i a t e d w i t h human h e m i b a l l i s m u s .  located  t o send  (Orlovsky,  t r a c e r PHA f o l l o w i n g  the subthalamic  (Shik e t  t o be c o e x t e n s i v e w i t h t h e  accident  reticular  o f MLR  formation  hypothalamic  i n t o t h e r a t s u b s t a n t i a innominata  a spontaneously  o f t h e SLR c a n be  1 9 7 3 ) . Thus, t h e SLR a p p e a r s  1 9 7 0 b ) . A n a t o m i c a l l y , t h e SLR a p p e a r s  ZI/LHA r e g i o n , l i k e  locomotion activity  stimulation  t o b o t h t h e MLR a n d r e t i c u l a r  zona i n c e r t a  locomotion  (Orlovsky, 1969). A l s o ,  destruction  made t o r u n a n d w a l k w i t h e l e c t r i c a l  but  bilateral  SLR-stimulated  associated with the thalamic preparation  al.,  of the  an a c u t e t h a l a m i c c a t . F u r t h e r , he f o u n d t h a t  lesion but  (SLR),  stimulation  picrotoxin  i n t o the  feline  l o c o m o t i o n w h i c h c o u l d be agonist)  i n f u s i o n . This  contained  within  the  SLR  blocked  data  SLR  e v o k e d b o t h a c t u a l and by  implicates  i n the  suggestion  that  s t i m u l a t i o n of the  ganglia-thalamic  f i b r e s . As  SLR  act  as  b e e n shown t o disease chorea  be  SLR  discussed  i n the  Skinner  activates  below, t h e  (Mogenson e t al.,  and  (1986)  basal  region  o f motor  of  en the  information  1985).  of the  (cf. Carpenter,  c o n s t i t u t e severe  major d e f i c i t s or  r e v i e w see Electrical  ( W e t z e l and  and  Skinner,  s t i m u l a t i o n of the  of various  al.,  n u c l e i of the  impairment begun  or  the  appear t o  Stuart,  be  1976;  1986).  i n the  lightly  cats with  basal  ganglia  anaesthetized bilateral do  l o s s of coordination  (Waller,  1930). T h e r e f o r e ,  these  globus p a l l i d u s produces  1 9 4 0 ) . Monkeys, dogs and  has  1978). A l t h o u g h  i n t e n t i o n a l nature  cat  progression  Huntington's  these diseases  Garcia-Rill  has  Parkinson's  associated with  locomotor responses  incapacitating  and  nuclei  i m p a i r m e n t s t o motor p e r f o r m a n c e ,  inconsistent  ablation  ganglia  s u c h as  n i g r a , p a r s compacta),  (caudate nucleus)  (Waller,  basal  l e a d t o movement d i s o r d e r s  of a postural  et  dendrites  locomotion  and  transduction  or degeneration  (Substantia  disorders  for  Garcia-Rill  or  Ganglia  Damage t o  the  will  a step  from l i m b i c systems  Basal  bodies  or entopedunculo-pedunculopontine nuclear  passant may  by  cell  (GABAA r e c e p t o r  a c t i v a t i o n of  c o n t r a d i c t s the electrical  muscimol  ^fictive'  1940; basal  Denny-Brown, ganglia,  while  not once 1966;  show locomotor Hinsey  important  to  the  initiation  o f voluntary locomotion,  the  s t e p p i n g mechanism i t s e l f  modulate locomotor  activity  ( M a r t i n , 1967) b u t p r o b a b l y  through  e x t r a p y r a m i d a l motor c i r c u i t r y  connections  and Skinner,  1986). In accordance  information,  the substantia nigra,  pars  a GABAergic p r o j e c t i o n  while  entopeduncular  1986;  also  and  glutamate) Skinner,  Limbic  and Skinner,  the basal ventral  anterior  may e x e r t some i n f l u e n c e  efferents with excitatory  appear t o connect  GABAergic  an as y e t u n s p e c i f i e d  amino a c i d s  w i t h t h e PPN/mMLR  (EAA) s u c h as  ( G a r c i a - R i l l and  Structures  aspects  s t r u c t u r e s have b e e n i m p l i c a t e d i n m o t i v a t i o n a l  o f locomotor  escaping neural  (possibly  ( C h i l d s and  1986).  Limbic  part,  thalamic nuclei,  t h e MLR, a s c o r t i c a l  neurotransmitter  pallidus  loop, v i a t h e centromedian,  lateral  has been  e t al., 1985),  (Garcia-Rill  McGeer e t al., 1 9 8 4 ) . I n a d d i t i o n ,  ventral  over  and g l o b u s  i m p i n g e on t h e PPN/MLR  ganglia-cortical  this  t o t h e PPN/MLR  1983; McGeer e t al., 1984; G a r c i a - R i l l  efferents  with  reticulata  Gale,  nucleus  with  i n c l u d i n g t h e PPN/MLR  (Garcia-Rill  shown t o s e n d  do n o t a p p e a r t o a f f e c t  from  circuit  behaviours  predators  underlying these behaviours  (SI) & l a t e r a l  1 9 8 5 ) . The  i s b e l i e v e d t o be, i n  ( B r u d z y n s k i a n d Mogenson,  r e g i o n s , t h e hippocampal  been demonstrated t o p r o j e c t innominata  as p r o c u r i n g f o o d o r  ( B r u d z y n s k i a n d Mogenson,  m e d i a t e d v i a t h e PPN/MLR  Two l i m b i c  such  formation  a n d amygdala,  to the subpallidal  p r e o p t i c area  32  (LPA)]  1985). have  area [substantia and n u c l e u s  accumbens  (NA)  Wu,  1 9 8 8 ) . The  1986,  projection  to  i n the  the  also  to  the  al.,  ZI/LHA al.,  ( G a r c i a - R i l l et  to  the  Skinner,  region,  1 9 8 5 ) . The (SLR)  i n turn,  p a r s compacta  Brudzynski  (e.g.  synaptic  and  antagonists  (e.g.  4)  et  Mogenson,  1985)  by  picrotoxin)  to  2)  3)  the  limbic  the  freely  substantia to  that  NA. increase  locomotor  ( f o r review,  see  significantly  of  (Jones and  with  1980)  SI  activity  these regions  major l o c o m o t i o n - a s s o c i a t e d c e n t r e s ,  region  Mogenson,  ZI/LHA a f t e r  above f i n d i n g s  NA  GABA  subpallidal  reduces the  et  i n j e c t i n g procaine,  Injection  i n t o the  l i m b i c motor i n t e g r a t i o n may  The  amphetamine i n j e c t i o n i n t o  locomotor a c t i v i t y  hyperactivity  PPN  and  (Mogenson  using the  nuclei  (Mogenson  of t h i s  agonists  1985),  i n t o the  n e u r o a n a t o m i c a l d a t a showing t h a t  that  PPN  PPN  increased  i n t o the  1985),  a l . , 1985). Combining the  the  1)  axonal transmission  i n j e c t i o n of procaine  picrotoxin-induced  to  to  studies  amphetamine)  and  sends  1980)  a l . , 1985).  importance  have found t h a t :  elicited  Mogenson,  (SI/LPA) i n c r e a s e d and  and  Mogenson,  reduced h y p e r a c t i v i t y ( B r u d z y n s k i and  Mogenson,  sends e f f e r e n t s  of  NA  cuneiform  sends a d o p a m i n e r g i c p r o j e c t i o n  ( B r u d z y n s k i and  which b l o c k s  1 9 8 3 b ) . The  sends a p r o j e c t i o n  i n j e c t i o n o f dopamine o r  dopamine r e l e a s e  activity  al.,  (Mogenson e t  support the  moving r a t . These s t u d i e s  NA  Mogenson  send a d i r e c t  J o n e s and  comes f r o m a v a r i e t y  Intra-accumbens  1985;  s u b p a l l i d a l region'' a l s o p r o j e c t s  1985). E v i d e n c e t o  nigra,  1986;  i n turn,  which,  motor c i r c u i t  al.,  p e d u n c u l o p o n t i n e and  s u b p a l l i d a l region  subpallidal et  and  (Mogenson e t  amygdala a p p e a r s t o  MLR  GABAergic e f f e r e n t s (Garcia-Rill  rat  (Mogenson  the are  i t appears  occur through t h i s  connected possible neural  to  circuit  ( B r u d z y n s k i and Mogenson,  1985/  Mogenson,  1984).  C o n c l u s i o n s and Purpose o f S t u d i e s i n the T h e s i s  The that,  survey  of the  literature  w h i l e a g r e a t d e a l i s now  mechanisms i n t h e CNS  control  elucidated.  F o r example,  oscillators  which are capable  the o s c i l l a t o r s  rhythmic  spinal  of producing the b a s i c  which comprise  the  oscillators  animals,  the  obligatory  role,  descending  tracts  vestibulospinal,  remain  system  as  lesion  r u b r o s p i n a l and  t o add  system.  However, l i t t l e  postural  and  Furthermore,  systems,  control  i s known a b o u t  more i s known a b o u t  impinging  the hodology  to play  systems o f p r i m a t e s  account  f o r the  occurrence  versus  of spinal  the and  to exert  knowledge i s a v a i l a b l e on t h e s e than  descending  about  the  t h e s e pathways.  lower  are  connections  i s known r e g a r d i n g t h e d i f f e r e n c e s between t h e  control  an  The  features to  pathways u t i l i z e  n e u r o t r a n s m i t t e r s which a c t t o c o n t r o l little  controlling  pathways  the exact  while only l i m i t e d  c o n c e r n i n g the n e u r a l elements  circuits  formation or i t s  corticospinal  "fine"  neurotransmitters the descending control.  reticular  abolishes voluntary locomotion.  thought  locomotor  v e r t e b r a t e s . In  pathway a p p e a r s  of the  be  t h e most c l e a r l y d e l i n e a t e d  i n non-primate  reticulospinal  to  unknown.  s u p r a s p i n a l pathways  are perhaps  and  rhythmic  c o r d . However, t h e n e u r a l  of descending  components o f t h e c o n t r o l these  much r e m a i n s  i t i s generally accepted that  i n the  origins  the p o i n t  known c o n c e r n i n g p a t h w a y s  of locomotion,  patterns exist  The  presented r e i t e r a t e s  Very locomotor  v e r t e b r a t e s which c o u l d  s t e p p i n g found  in a l l  v e r t e b r a t e s except Higher  order structures  basal ganglia, vestibular) exert  comparatively  As  system,  little  sensory systems  systems  regarding the  control.  o u t i n complex mammalian s y s t e m s  animals  locomotion  (Dietz,  studies  have  (e.g. c a t ,  rat)  1 9 8 7 ) . The u s e o f  imposes c o m p l i c a t i o n s t o t h e s t u d y o f motor  (e.g. i n t r a g i r d l e  coordination,  may,  i n part,  bird  seemed t o me t o be i d e a l  gait  conversion)  that  be overcome by t h e s t u d y o f a b i p e d a l s y s t e m .  The  f o r the study o f locomotor  b e h a v i o u r . L i k e humans, t h e b i r d overground  appear t o  s u p r a s p i n a l pathways, b u t  d e s c r i b e d above, t h e m a j o r i t y o f l o c o m o t o r  quadrupedal  regions,  (e.g. t r i g e m i n a l ,  (e.g. cerebellum)  i s known w i t h c e r t a i n t y  employ q u a d r u p e d a l  systems  i n c l u d i n g the locomotor  over the descending  of this  been c a r r i e d that  limbic  and comparator  control  specifics  primates.  locomotion. Also, l i k e  i s a true biped during humans, presumed  interactions  between f o r e l i m b s a n d h i n d l i m b s w h i c h o c c u r i n q u a d r u p e d a l animals  are reduced  or absent  except  during the t r a n s i t i o n  walking to f l y i n g .  The two i n d e p e n d e n t  a l s o make t h e b i r d  an i d e a l model f o r t h e s t u d y o f l o c o m o t o r  behaviour, neural  as i t may be p o s s i b l e t o more e a s i l y  circuitry  involved  l o c o m o t i o n . Perhaps the c o r t i c o s p i n a l control  i n t h e s e two d i f f e r e n t  the c o n t r o l  i s o l a t e the modes o f  which c o m p l i c a t e s t h e s t u d y o f motor  i n mammalian s p e c i e s a n d p r i m a t e s  strongly  locomotion  most i m p o r t a n t l y , t h e b i r d does n o t p o s s e s s  tract  Webster and Steeves, absence  modes o f a v i a n  from  1988;  (Cabot  R e i n e r and K a r t e n ,  e t al.,  1982;  1982). T h i s  i m p l i c a t e s more c a u d a l b r a i n s t e m s t r u c t u r e s i n  o f l o c o m o t i o n a n d a l l o w s one t o s t u d y a complex  35  motor system the  intact  equivalent the  level  that  state.  i s devoid of c o r t i c o s p i n a l Lastly,  b i r d s possess  t o a l l mammalian v e r t e b r a t e s of the b a s a l g a n g l i a  making p o s s i b l e  the  comparison  only  v e r t e b r a t e motor systems, aspects of motoricity,  but  circuitry  o f h i n d - and m i d b r a i n  of neuronal also  including  even i n  ( i n c l u d i n g primates)  to  thus locomotor  range.  above a t t r i b u t e s make t h e b i r d  f o r the e l u c i d a t i o n  motor  ( R e i n e r e t a l . , 1984),  mechanisms a c r o s s a b r o a d p h y l o g e n e t i c The  CNS  influences,  an e x c e l l e n t  elements  f o r the  locomotor  model  not  controlling  study  of  other  development  and  repair. Prior  to the beginning of t h i s  literature  indicated that  physiology  and  locomotion  in birds  (Eidelberg,  1 9 6 0 ) . My  Branta it  was  i s an e x c e l l e n t  available  flier.  utilized  and  i n some o f t h e  1984;  1 9 8 7 ) . The  as w e l l  Further, i t i s a large i s easy  and  that  absence  descending Sholomenko Canada  ten  to handle  domesticated  the domesticated acute brainstem  and  animal  as a r e m a r k a b l e animal,  control  goose,  as t h e main e x p e r i m e n t a l  walking b i r d  f o r study,  platyrhynchos  e t al.,  chosen  an e n d a n g e r e d s p e c i e s . The Anas  controlling  ( T a r c h a n o f f , 1895/  initiation  ( W e i n s t e i n e t al.,  1987a,b; S t e e v e s  canadensis  distance  the  s t u d i e s have e x a m i n e d a s p e c t s o f t h e s u p r a s p i n a l  avian locomotion  Steeves,  known a b o u t  1981), w i t h t h e e x c e p t i o n  ("spinal stepping")  mechanisms r e s p o n s i b l e f o r t h e of  was  the  o f m a k i n g s t e p p i n g movements i n t h e  supraspinal input  Cate,  little  of  anatomy o f s u p r a s p i n a l s t r u c t u r e s  b i r d s were c a p a b l e of  very  work, a r e v i e w  as  long  i s readily  in captivity non-flying, Brandies  and  i s not  Pekin  duck,  g o o s e were  stimulation  also  experiments  to  determine the  the  applicability  goose t o o t h e r My  previous  avian  of the  s t u d i e s have i n c l u d e d :  electromyographic  techniques  muscles best  respectively. i n c l u d e the  The  the  stance  cruris  p e c t o r a l i s muscle  lateralis  2)  using  the  selective  determine the hindlimb  and  iliotibialis  descending  low  mid-  and  i s e s s e n t i a l f o r locomotion  in  the  the  mammals, t h e r e b y  define  flexor  (ITC)  1987b) and  has  low  and  Results  in  to  acute  from  descending  in  these the  i n both  reticulospinal  3)  current  which are  pathway  d e f i n i n g regions stimulated,  i n t e n s i t y . Mapping o f  determined the  equivalent  to those  p r o v i d i n g a b e t t e r understanding  37  in  maintain  of and  the  produce these  l o c a t i o n of locomotor  i n f l u e n c e s which i n i t i a t e ,  as  v e n t r a l s p i n a l cord  w h i c h , when e l e c t r i c a l l y  avian brainstem  supraspinal  was  Steeves,  sites  i n c l u d e the  and  pathway most s t r o n g l y i m p l i c a t e d  a d i f f u s e p r o j e c t i o n i n the  l o c o m o t o r movements a t stimulation  the  locomotion  hindbrain  phase  Muscles which  stimulated preparation.  Further,  (Sholomenko and  patterns  flight  i n both c h r o n i c a l l y maintained  funiculi  as  and  s p i n a l c o r d pathways e s s e n t i a l t o  ventral  travelling  using  thoracic s p i n a l cord  d e m o n s t r a t e d t h a t motor i n f o r m a t i o n  to  walking  cranialis  studies  essential  1984)  of  mammalian s a r t o r i u s m u s c l e ) , r e s p e c t i v e l y ,  brainstem  preparations.  index  (major w i n g d e p r e s s o r )  (DM)(wing l e v a t o r ) .  and  e t al.,  d e f i n e the  (PECT)  l e s i o n s of the  locomotion  decerebrate  flight  swing phase o f w a l k i n g  (FCL)  (synonymous w i t h  d e f i n i n g an  to determine which f o r e l i m b  muscles which best  p h a s e and  1)  (Weinstein  d e f i n e the  d e l t o i d e u s major muscle  findings in  species.  normal locomotor muscle p a t t e r n s  hindlimb  experimental  sites  found i n the modulate  locomotion  in birds  stimulation from  the  sites  found  e t al.,  t o date  and  r e g i o n appears locomotor  tract t o be  strip  2)  of the  i n the v e n t r a l  reticular  The  pontomedullary et  al.,  and  central  reticular  slightly  nuclei  medial  and  to the  3)  a  lateral  above f i n d i n g s have d e m o n s t r a t e d t h a t s t r u c t u r e s  t h e s i s was  f o r a v i a n motor c o n t r o l  to further  behaviours.  The  functional  repair  (CNS)  s t i m u l a t i o n was locomotor  of t h i s  2,  or  to those  s t u d i e s found and  c o n t r i b u t e to the  control  prerequisite  circuitry  found  in this  other regions i n of  of neural c i r c u i t r y  i s a necessary  injury  In Chapter  purpose of the  characterization  locomotion  are s i m i l a r  c h a r a c t e r i z e these  a v i a n b r a i n w h i c h may  system  This  of the h i n d b r a i n which l i e  which l i e s  o t h e r v e r t e b r a t e s . The  controls  within  nucleus.  responsible  the  t o and  t r i g e m i n a l system.  gigantocellular  formation  evoking  extending  or Probst's T r a c t of G a r c i a - R i l l  i n the midbrain  spiriform  a strip  subjacent  descending  w i t h i n t h e d o r s a l and v e n t r a l  in  i n c l u d e : 1)  e q u i v a l e n t t o t h e mammalian  (PLS  sites  magnocellular  region  1987). Locomotion  c a u d a l pons t o c a u d a l m e d u l l a  the nucleus  1983b)/  (Steeves  to  locomotor  which  the  following central  nervous  degeneration.  a systematic survey  performed  i n an  r e g i o n s w h i c h may  using focal  attempt  to l o c a l i z e  exert control  over the  electrical other  avian  regions  d e s c r i b e d p r e v i o u s l y . Three p r e v i o u s l y u n c h a r a c t e r i z e d locomotion-evoking found.  One  region l i e s  intercollicularis be  electrical  (ICo)  s t i m u l a t i o n r e g i o n s have b e e n  i n c l o s e p r o x i m i t y t o the of the t e c t a l  l o c a l i z e d t o the medial  midbrain  38  midbrain.  reticular  nucleus The  second  formation  can  (MRF). A  third  site  medullary  lies  w i t h i n the  medial  longitudinal  F o l l o w i n g the defined  locomotor  performed  localization  necessarily  f o r two  locomotion  from  locomotion  elicited  locomotion  a locomotor  selective may  reversible  of  between  o f axons o f p a s s a g e .  of d i f f e r e n t  i n v o l v e d i n the  injection  locomotion-evoking  locomotor  circuitry  d i s c u s s e s the r e s u l t s  the and  the  of  direct  of c h o l i n e r g i c neurotransmitter agonists  locomotion-evoking  locomotor  c e n t r a l nucleus  electrical  stimulation  long l a s t i n g  mesencephalic  introduction  (PLS), d o r s a l p a r t o f t h e  Injection  of agonist i n t o the  reticular  formation  (MRF)  the  medullary  medial  the t h r e s h o l d  stimulated locomotion.  4 d e s c r i b e s and  discusses the r e s u l t s  of y-aminobutyric  of e l e c t r i c a l Cnv,  reduced  and  central  MLF.  for e l e c t r i c a l l y Chapter  strip  (Cnd), v e n t r a l p a r t o f t h e m e d u l l a r y  (Cnv), and  Cnd,  activation  ( a n t a g o n i s t ) l o c o m o t i o n when i n t r o d u c e d i n t o  pontobulbar  PLS,  was  of neurotransmitter receptors  Cholinergic muscarinic agonists e l i c i t e d  nucleus  these  provide information concerning both  antagonists into  variety  survey  neurochemical  stimulation  3 d e s c r i b e s and  intracerebral  sites.  into  n e u r a l pathways w h i c h c o n t a i n t h e s e n e u r o t r a n s m i t t e r s .  Chapter  and  this  were  region should d i f f e r e n t i a t e  activation  injection  neurotransmitters potential  by  rostral  electrophysiologically-  o f neurochemicals  First,  and  (MLF).  of experiments  incomplete,  reasons.  e v o k e d by  neurochemicals  of the  regions, a series  undertaken  Second,  fasciculus  using microinjection  r e g i o n s . While  and  c o n f i n e s of the pontine  pontine  acid  39  the  (GABA) a n t a g o n i s t s i n t o  stimulation-defined sites, reticular  from  formation  (RP)  including and  ICo.  a the  Antagonist  injection  evoked l o n g  lasting  l o c o m o t i o n ' w h i c h was  Chapter 5 d e s c r i b e s  transiently  r e v e r s e d b y GABA.  the  f r o m m i c r o i n j e c t i o n o f e x c i t a t o r y amino a c i d a n d  results  Substance P i n j e c t i o n Injection  a variety  of the glutamatergic  (NMDA) i n t o elicited, induce,  into  sites  o f locomotor  agonist  regions.  N-methyl-D-aspartate  i n c l u d i n g t h e PLS, Cnd, Cnv, MLF a n d MRF  or reduced  locomotion.  the e l e c t r i c a l  threshold necessary t o  These e f f e c t s were r e v e r s i b l e w i t h t h e  glutamate antagonist  glutamic  acid  diethyl  Injection  o f Substance P i n t o t h e pontine  reticular  formation  for e l e c t r i c a l l y  and d i s c u s s e s  elicited  walking  stimulated  ester  (GDEE).  and m e d u l l a r y  or reduced  the threshold  locomotion.  P h a s i c p e r i p h e r a l a f f e r e n t i n p u t h a s b e e n shown t o have a role  i n locomotor c o n t r o l i n a v a r i e t y  Chapter  6 ) . However, t h e e x t e n t  important  i n avian  Therefore,  locomotion  studies designed  o f v e r t e b r a t e s (see  t o which t h i s  has n o t been  i n p u t may be  determined.  t o examine w h e t h e r p h a s i c p e r i p h e r a l  o  afferent  i n p u t was e s s e n t i a l  undertaken  (Chapter  f o r avian  6 ) . My r e s u l t s  p a t t e r n s were e v o k e d by b o t h  bird was  demonstrate t h a t  electrical  o f s e v e r a l mid- and h i n d b r a i n  sites  locomotor p a t t e r n s  and c h e m i c a l  x  found  i n high  These r e s u l t s The  decerebrate  are discussed  multilevel  locomotor stimulation  i n the decerebrate  ( f i c t i v e ' p r e p a r a t i o n ) . Furthermore, spontaneously  x  fictive'  were  paralyzed  locomotion  locomoting  birds.  i n Chapter 6.  organization of neural c i r c u i t r y  subserving  locomotor c o n t r o l has been demonstrated by s e l e c t i v e t r a n s e c t i o n of the neuraxis described  i n a variety  i n the general  o f decerebrate  p r e p a r a t i o n s . As  i n t r o d u c t i o n (see Locomotor Regions and  Locomotion-related  Structures), decerebration to a l e v e l  p r e s e r v e s t h e mammalian s u b t h a l a m i c spontaneous locomotion  organization exists  w h i c h may  exert control  in birds,  over  locomotor  o f d e c e r e b r a t i o n were p e r f o r m e d  and  unparalyzed  decerebrate  animals  behaviour,  lying  near  r e g i o n of the  (Chapter  as  and  a region  varying effects  i n both  levels on  paralyzed  7). Results  from  i n mammals, s t r u c t u r e s  subthalamic  spontaneous locomotion  whether  to identify  non-spontaneous locomotion  s t u d i e s show t h a t i n b i r d s ,  subserve  and  allows  determine  t o examine t h e i r  these  the  region  i n t h e p r e p a r a t i o n . To  a similar  spontaneous versus  locomotor  which  nucleus  appear  to  removal o f these s t r u c t u r e s  by more c a u d a l t r a n s e c t i o n e l i m i n a t e s t h i s  spontaneous  activity.  The Decerebrate P r e p a r a t i o n  The utilized the  unanaesthetized i n a broad  study  Bars,  decerebrate  range o f n e u r o b i o l o g i c a l s t u d i e s  of high t h r e s h o l d t a c t i l e  1979/  Kajander  and  Giesler,  ( e . g . E l d r i d g e e t a l . , 1985/ locomotor Macht,  control  1958/  p r e p a r a t i o n has  research  Budakova and  stimuli  1987),  (e.g. A o k i Shik,  1970/  Garcia-Rill,  1983/  Garcia-Rill  and  Skinner,  1987/  Grillner  e t al.,  1985/  K a z e n n i k o v e t al.,  Jell  1970a,b, 1984/ al.,  1972a,b; S e l i o n o v and  Sherrington, 1987/  and  Steeves  1910, and  1915/  Jordan,  Shik,  Shik 1980/  41  research  (submitted)) Mori,  Le  and  1981/  Bard  and  E i d e l b e r g e t a l . , 1981b;  e t al.,  Shik,  and  including  ( e . g . B e s s o n and  respiration  Funk e t al.,  been  1983a,b,c/ 1973/  Garcia-Rill  Hinsey  e t al.,  1983a,b; O r l o v s k y , 1984/  Shefchyk  e t al., Steeves  1966/  et  1930/ 1969,  al.,  Sholomenko e t  e t al.,  1987;  V i l l a b l a n c a , 1962; W a l l e r , 1940). D e c e r e b r a t e  a n i m a l s are d e v o i d  o f any c o n c i o u s p e r c e p t i o n o f p a i n , a l l o w i n g e x p e r i m e n t a l m a n i p u l a t i o n s which are not a c c e p t a b l e i n i n t a c t , u n a n a e s t h e t i z e d a n i m a l s which are unable t o " i n d i c a t e o r a r r e s t t h e onset o f s u f f e r i n g " Sternbach, The  (e.g. p a r a l y z e d )  ( W a l l , 1975; W a l l  and  1976).  f o l l o w i n g q u o t a t i o n , which s u p p o r t s t h e view t h a t  d e c e r e b r a t e a n i m a l s are d e v o i d o f p a i n , (Adams, 1980)  relates to  human p a i n p e r c e p t i o n . "Perception  of  impulses  at  is  concious  there  study  has  nervous  the  not  pain.  thalamocortical awareness  informed  apparatus abolished  thalamus  on  one  by  and  that  parietal of This  and  cortex complete.  The  instance of  of  view  the  conscious comprise  in  the  an  order  painful  said  and  for  and  stimulus)  unconscious indivisible  nervous  It  is  for  responses process."  of  sensation  the of  the  Probably  sensation  a and to (in  (awareness  been  abandoned and  to  the reaching  thalamus  perception  perception,  not  experience  of  the  impulses  attributes  a sensory  of  including  that  between  has  system Clinical  localization  separation  pain  localization  process.  the  of  stimulus.  i s necessary  pain)  sensation,  the  oversimplification.  traditional  that and  an  of  arrival  pain  exact  relationship  awareness  nature  the  of  cortex  seems  exist  of  i s often  intensity  harmonious  must  level  the  awareness  the  the  t o t a l hemispherectomy,  It  create  close  a  side.  thalamus  appreciation  of  upon  t h i s mental  the  the  of  us  for  entirely  sensation.  Only  a pain  the  be this of  in various stimulus  the favor  T h i s view i s f u r t h e r supported  by t h e f i n d i n g  moving r a t w i t h v a r y i n g l e v e l s  of decerebration  and  brainstem  painful  stimuli,  affective 1968;  support  reflex  while  of pain  In r e g a r d t o p a i n procedure, surgical  responses. conscious incision pain  (Emmers,  of brain tissue  does n o t e l i c i t  1981). In t h i s  oxide  of local  local  thesis,  i n h a l a t i o n anaesthesia  completion  increase  until  procedures,  animal  2, e l e c t r i c a l  oxide  p o i n t s and i n c i s i o n o f the experiment ( f o r  s e e M a t e r i a l s and Methods, (e.g. w r i t h i n g ,  elevated heart  rate)  were  ( s e e APPENDIX I I ) and, a s  s t i m u l a t i o n c a u s e d no  rate or blood pressure,  evoked by t h e s t i m u l a t i o n e l i c i t e d changes.  s i t e s and  of the decerebration  the termination  i n any d e c e r e b r a t e  i n heart  direct  removal o f h a l o t h a n e / n i t r o u s  elevated blood pressure,  shown i n F i g u r e  under  with  anaesthetic at a l l i n c i s i o n  of a l l surgical  procedures,  were p e r f o r m e d  C h a p t e r s 2 , 3 , 6 , 7 ) . No s i g n s o f d i s c o m f o r t  observed  pain  anaesthetics at  a l l surgical  anaesthetic at pressure  s i t e s was c o n t i n u e d  vocalization,  1975).  are often performed i n  o n l y t h e use o f l o c a l  p r o c e d u r e and subsequent  details  and B l a c k ,  i s a v a i l a b l e f r o m human s t u d i e s t h a t  points. Following  anaesthesia,  (Charpentier,  such p a t i e n t s never r e p o r t t h e p e r c e p t i o n o f  halothane/nitrous  pressure  support  from t h e d e c e r e b r a t i o n  decerebration procedures,  infiltration  and c o r t e x  see Loeser  Many n e u r o s u r g i c a l p r o c e d u r e s  sites;  including  levels,  resulting  patients with  reactions to  alertness, respectively  strong evidence  manipulation  that the medulla  and f l i g h t  the rhinencephalon  and i n t e l l e c t u a l  f o r review  and s t a r t l e  i n the freely  while  distinctive  the  significant locomotion  cardiovascular  Figure rate  2.  Electromyographic  changes r e s u l t i n g  from  region of the descending stimulation intensity pressure  trace  (BP)  stimulation  d e m o n s t r a t e d by right  muscles) muscles  on t h e  and  left  (major  (LITC)  (HR)  hip flexor  shown) it  also  returning to resting  d u r i n g the  levels  interval  flapping).  44  not  constant  appeared  t o d i s t i n g u i s h t h e HR  observed  wing  left  as  (LPECT)  depressor cranialis  mammalian (see  calibration  returned to resting shown). The  until  levels heart  the t h r e s h o l d  to increase with  f o l l o w i n g the t r i a l  (nb. d u r i n g s t r o n g w i n g f l a p p i n g ,  difficult  c a n be  and  the  of  at  of locomotion,  increased  ( r e t u r n t o r e s t i n g BP  reached  the beginning reached  from  (major  and  The  Blood  (RITC) i l i o t i b i a l i s  remained r e l a t i v e l y was  was  synonymous w i t h t h e  locomotion  right.  from  onset  records  right  heart  ramped s t i m u l a t i o n  constant  the blood pressure  with the  locomotion  exercise,  and  nucleus.  80uA a t t h e  Upon t h e  electromyographic  f o l l o w i n g the t r i a l  for  to  (RPECT) p e c t o r a l i s m u s c l e s  at r i g h t )  rate  left  and  s t i m u l a t i o n i n the  and  t h r e s h o l d f o r locomotion  s a r t o r i u s muscle), bar  trigeminal tract  60uA i n t e n s i t y .  approximately  and  ramped e l e c t r i c a l  remained r e l a t i v e l y  until  blood pressure  (STIM) d e m o n s t r a t e s t h e  OuA  from  activity,  movement a r t i f a c t  signal.  However, t h e  between b o u t  of  (not makes  signal  strong  eouA  8 0u A  OmmHg  HR I 1MC I  Further animals from  indirect  were n o t  evidence  capable  s t u d i e s examining  evoking  of p e r c e i v i n g  respiratory  locomotion with brainstem  [electrical locomotor  and  neurochemical  region  stimulation submitted) responses  - trigeminal also  animals.  nucleus  noxious  observed  s t i m u l u s come  c h a n g e s as a c o n s e q u e n c e stimulation. -  In b o t h  and  I I and  tract  of  cat  subthalamic [electrical  (Funk e t a l . ,  F i g . 2], the  ventilatory  or chemical s t i m u l a t i o n - i n d u c e d to those  Taken t o g e t h e r , t h e  contention that  decerebrate  e t a l . , 1985)] and b i r d  see A p p e n d i x  to e l e c t r i c a l  that  a painful  stimulation  (Eldridge  l o c o m o t i o n were s i m i l a r  results  demonstrating  observed  above e v i d e n c e  s t i m u l a t i o n was  in this  i n unoperated supports  not  intact  the  r e s p o n s i b l e f o r the  study.  NOMENCLATURE  To p r e v e n t  c o n f u s i o n c o n c e r n i n g s t r u c t u r e s w h i c h have  homologous n o m e n c l a t u r e  but  are not  equivalent i n the  v e r s u s t h e mammalian l i t e r a t u r e ,  I have u s e d  where a d v i s a b l e . Thus, t h e  avian  Nucleus  tegmentipedunculopontinus,  pars  compacta  compacta  (SNc)  the  lenticularis  ansa  nucleus,  different and  (nAL)  will  exist  be- c a l l e d  called  the  subthalamic  ( B r a u t h e t a l . , 1 9 7 8 ) . Where  I have u t i l i z e d  the  avian  a p p r o p r i a t e mammalian c o u n t e r p a r t  with  nomenclature (e.g.  by  pars  avian nucleus  between a v i a n and mammalian s t r u c t u r e s  nomenclature,  p r o v i d e d the  be  will  substantia nigra,  (Brauth et a l . , 1978). A l s o , t h e  i t s mammalian e q u i v a l e n t  homologies  t h e mammalian names  (TPc)  t h e name o f i t s mammalian e q u i v a l e n t , t h e  avian  of  iliotibialis  cranialis  (ITC) m u s c l e  mammalian s a r t o r i u s m u s c l e )  i s equivalent  (Weinstein  47  e t al.,  to the  1984).  CHAPTER 2  ELECTRICAL STIMULATION OF MESENCEPHALIC AND PONTINE REGIONS ELICITS LOCOMOTION IN DECEREBRATE BIRDS  48  INTRODUCTION  The by  initiation  supraspinal  species  structures  was  1981;  during  forelimb birds  and  birds  do  to the  are  pathways  not  al.,  by  these  are i n v e s t i g a t i n g birds display  f r o m t h o s e u s e d by  and  may  of  a  wing  the  legs  generators  a l s o suggest t h a t  c o n t r o l l e d by  ( J a c o b s o n and  different  Hollyday,  possess a telencephalo-spinal  u n l i k e most v e r t e b r a t e s ,  the  of  in  two  descending  1982).  Second,  p r o j e c t i o n analogous  (Cabot  b i r d s are  e t al.,  1982).  t r u e b i p e d s whose  r e s e m b l e human w a l k i n g  (Weinstein  1984).  Earlier  reports  f r o m our  laboratory  1987;  Sholomenko and  Steeves,  1987a,b) have d e m o n s t r a t e d  focal  electrical  the  little  suggests a f u n c t i o n a l uncoupling  overground locomotor patterns et  1 9 8 7 ) . We  mammalian c o r t i c o s p i n a l t r a c t  Finally,  role played  s p i n a l locomotor p a t t e r n  1962),  generators  supraspinal  the  functional activity  flight  walking. This  (ten Cate,  pattern  al.,  between t h e  hindlimb  vertebrate  r e c e n t l y , however, v e r y  f o r several reasons. F i r s t ,  involved during bipedal  i n many  c o n t r o l of locomotion i n b i r d s  Steeves et  separation  muscles  1986). U n t i l  neural  locomotion  strong  been s t u d i e d  a v a i l a b l e concerning  i n the  (Eidelberg,  c o n t r o l o f s p i n a l l o c o m o t o r mechanisms  s t r u c t u r e s has  (McClellan,  information  avian  and  low  bipedal stepping  of avian  b i r d preparation  can  elicit  locomotor behaviours.  a l t e r n a t i n g stepping, with  e t al.,  stimulation of d i s c r e t e hindbrain  decerebrate  repertoire  (Steeves  bipedal  w i n g f l a p p i n g and  flying  The  alone.  that  regions  the  in  entire  behaviours  synchronous  1986,  include  hopping,  One  locomotion-evoking  ventromedial pontomedullary the g i g a n t o c e l l u l a r lay  dorsolaterally  (LRF),  r e g i o n was reticular  reticular  (TTD)  Retrograde  formation  (see C h a p t e r  tracing  3,  Figs.  to both  cervical  1987a; W e b s t e r and in a variety  Grillner,  ( M o r i e t al., (Eidelberg neurons  and  Steeves,  stingray  1975), 1978;  e t al.,  turtle  S h i k and  p l a y a major r o l e oscillators  motor p a t t e r n  (Sholomenko and  Grillner, The  t o be  1985;  dorsolateral  e t al.,  Yagodnitsyn,  1977)  1980), and  (PLS)  seen  control  Shik,  1984;  f o r review  region also  monkey  of  f o r the  spinal basic  The  above e v i d e n c e  formation  circuitry  1987;  s e e M c C l e l l a n , 1986) locomotion  strongly  c o n s e r v a t i o n o f b r a i n s t e m and  1960,  1988).  ( S t e e v e s e t al.,  elicited  cat  1987b; t e n Gate,  r e g i o n of the r e t i c u l a r  i n cats  fish  reticulospinal  which are e s s e n t i a l  Dubuc,  and  telepst  t h e a v i a n homologue o f t h e mammalian p o n t o b u l b a r  strip  this  (Kazennikov  Steeves,  i n birds,  (McClellan  1979),  that  project  (Steeves et  These r e s u l t s  i n the descending  cord rhythmic  Rgc, sites,  cord  lamprey  1981b) d e m o n s t r a t e d  tract  stimulation  stimulation  ( L e o n a r d e t al.,  formation  trigeminal  bodies i n  1987).  second  10).  lumbar s p i n a l  of species i n c l u d i n g  1984),  ( K a s h i n e t al,  1962;  reticular  9 &  neuronal c e l l  c o - l o c a l i z e d with locomotion-evoking directly  (specifically,  combined w i t h e l e c t r i c a l  that  the  (Rgc)), while the  within the p a r v o c e l l u l a r  s t u d i e s demonstrated  as  formation  subjacent to or w i t h i n the descending  and n u c l e u s  al.,  located within  locomotor  S e l i o n o v and stimulation  in birds.  suggests  spinal  and  appears  a h i g h degree  c o r d motor  a c r o s s a broad p h y l o g e n e t i c range  of  neuronal  of species.  To  of  further t e s t t h i s hypothesis conservation  of  circuitry  and  observed i n the  c a r r i e d t o more r o s t r a l b r a i n stimulation regions  i n the  of the  counterparts  pons and  focal  p o n s . Two within  centres  the  localized  stimulation  within  the  dorsal  confines  electrical examine avian  regions,  of  locomotion could  regions  were l o c a l i z e d t o t h e  to the  n u c l e i of the  to the  i f  mesencephalic  of the avian  medial mesencephalic r e t i c u l a r  (Ipc)  pons i s  utilized  determine  the  locomotor  localized.  second i n c l o s e p r o x i m i t y isthmal  of the  f i n d i n g s demonstrate that  electrical  we  mammalian l o c o m o t o r  equivalents be  m e d u l l a and  systematically  mesencephalon to  o f more r o s t r a l  (MLR), c o u l d  Our  structures,  decerebrate b i r d to  including possible region  examine t o what e x t e n t  midline  of the  of the  medial  51  evoked  mesencephalon midbrain,  formation  intercollicular  t e c t u m . The  be  pontine pons and  and  one  (mMRF) and  (Ico) site  by  a  and was  rostral  medulla  longitudinal fasciculus  (MLF).  MATERIALS AND  METHODS  Surgery  Each b i r d  ( e i t h e r a Canada goose, Branta  P e k i n duck, Anas  was  platyrhynchos)  s u r g i c a l procedures w i t h halothane  a n a e s t h e t i z e d throughout a l l (1-3%) and n i t r o u s o x i d e  (20-30%) a d m i n i s t e r e d t h r o u g h an e n d o t r a c h e a l tube The a n t e r i o r a i r sac was (flow through)  cannulated to f a c i l i t a t e  ventilation  (UDV)  or a  canadensis  (Figure 3). unidirectional  o f t h e lungs w i t h 0 /C0 2  2  (95%/5%). The c a r o t i d a r t e r y and j u g u l a r v e i n were c a n n u l a t e d u n i l a t e r a l l y f o r m o n i t o r i n g b l o o d p r e s s u r e and i n f u s i o n r e s p e c t i v e l y . Body temperature temperature  fluid/chemical  was m o n i t o r e d w i t h a  probe i n s e r t e d i n t o t h e oesophagus and  (39-41°C) v i a a r e c t a l c o o l i n g / w a r m i n g  maintained  probe.  The b i r d was t h e n f i x e d i n a s t e r e o t a x i c head h o l d e r and t h e body s u p p o r t e d i n a s l i n g mounted over a m o t o r i z e d t r e a d m i l l . F o l l o w i n g a craniotomy,  a s u c t i o n d e c e r e b r a t i o n was  performed  a l o n g a p l a n e e x t e n d i n g d o r s a l l y from t h e c a u d a l margin o f t h e habenular nucleus t o the ventrocaudal p o r t i o n of the o p t i c chiasm. To p r e v e n t b l o o d l o s s d u r i n g t h e d e c e r e b r a t i o n procedure i n t h e geese, b l o o d p r e s s u r e was t r a n s i e n t l y d e p r e s s e d  by  i n t r a v e n o u s ( i . v . ) i n f u s i o n o f sodium n i t r o f e r r i c y a n i d e (nipride)  (15mg/100ml) i n 10% d e x t r o s e s o l u t i o n . In ducks,  d e p r e s s i o n o f b l o o d p r e s s u r e was n e c e s s a r y . A n a e s t h e s i a  no  was  d i s c o n t i n u e d f o l l o w i n g d e c e r e b r a t i o n and t h e b i r d s were a l l o w e d a minimum o f 30 minutes f o r a l l e f f e c t s o f t h e a n a e s t h e t i c t o wear o f f b e f o r e any form o f b r a i n s t i m u l a t i o n was 52  initiated.  All  pressure  points  routinely general  infused  decerebrate  ear bars)  with  anaesthetic  above u s u a l l y  and  (e.g.  and surgical  xyolocaine  removal.  The l e v e l  however,  reflex  electromyographic  percutaneously  responses  cranialis al.,  (ITC)  major d e p r e s s o r s  flight,  t o deep  normal.  muscle a c t i v i t y  (Weinstein e t  t h e PECT m u s c l e s a c t i n - p h a s e  (synonymous t o t h e mammalian s a r t o r i o u s m u s c l e s ) and a l s o  on.  ( G r a s s P15/Framp) a n d f i l t e r e d on an o s c i l l o s c o p e  ( G o u l d ES100B) a n d t a p e  as t h e  legs  f u n c t i o n as t h e  a s weak knee e x t e n s o r s . A l l EMGs were  recorded with the t r e a d m i l l  monitoring  implanted  o f t h e w i n g s . The ITC m u s c l e s o f t h e  major h i p f l e x o r s  pressure  (PECT) a n d i l i o t i b i a l i s  muscles t o monitor  1984). D u r i n g  i n the  (EMG) e l e c t r o d e s were  i n the p e c t o r a l i s  after  of transection described  e l i m i n a t e d spontaneous locomotion  animal,  were  (2%)  hydrochloride  f o o t web p i n c h s t i m u l a t i o n a p p e a r e d Bipolar  sites  EMG s i g n a l s were (band p a s s  amplified  200-10K Hz)  a n d r e c o r d i n g on c h a r t  prior to recorder  (Akai)(Figure 3).  Brain Stimulation  Focal e l e c t r i c a l the  avian brainstem  Pekin  was c o m p l e t e d  d u c k s . Two t y p e s  utilized. steel  stimulation of localized  The f i r s t  electrode  impedance  on 16 Canada g e e s e a n d 11  o f m o n o p o l a r s t i m u l a t i n g e l e c t r o d e were  t y p e was a c o m m e r c i a l l y  (Kopf model SNE 300,  60-70Kfi)  0.0762mm s t a i n l e s s  while the s t e e l wire  impedance = 60-70kfi)  regions within  through  second  available  t i p diameter  stainless  .= 0.1mm,  was c o n s t r u c t e d b y i n s e r t i n g  (exposed  t i p l e n g t h =s 0.1mm,  one b a r r e l  o f a p u l l e d three  53  -  barrel F  Pi.  f4  Broin  Stimulation  Exper i m e n t a l A p p a r a t u s  head holder  E.M.G movement potentiometer  inhatat ion anesthetic i n t e r n a l carotids ligated ventilatory outflow  treadmill  55  D  micropipette stimulation  (total trials,  undertaken with  (Grass  the  s q u a r e wave p u l s e current  t i p d i a m e t e r = 0.1mm). C o n s t a n t  strength  G r a s s M o d e l CCU1A) were  following standard  duration =  Stimulation  M o d e l S88/  stimulation  = 1.0-2.0ms; p u l s e  trials  were u n d e r t a k e n by  incrementally  electrode  Zweers,  1971)  i n t o the  current  i n t e n s i t y o f 50-100uA. When l o c o m o t i o n was  current  i n t e n s i t y was  t h r e s h o l d was  s t e r e o t a x i c a l l y (Karten brainstem while  reduced to  r e a c h e d . The  zero  and  optimal  then  t h e n e s t a b l i s h e d by  the  electrode  where c o o r d i n a t e d  lowest  recording  activity,  neuroanatomical by end  passing  the  the  stimulation site  identification  a direct  current  with  intravenous  KC1.  o f 2M  b r a i n s t e m was  paraformaldehyde,  then placed  i n two  marked  4 days. S e r i a l  coronally  on  sections,  at  with  the  l e s i o n made  f o r 5 seconds. At  deeply  placed  sucrose  lowering  for  electrolytic  anaesthetized a  f o r at (pH  least  =7.4).  (pH  (5%  2 days i n It  was  (25%  =7.4)) f o r a t  50um t h i c k n e s s ,  a f r e e z i n g m i c r o t o m e , mounted on  the  bolus  cyroprotectant  sucrose/10% glycerine/0.1M phosphate b u f f e r least  tip position  electromyographic  phosphate b u f f e r  changes o f  increased  slowly  s a c r i f i c e d with  removed and  0.1M  an  a n i m a l was and  4%  slowly  the  1987).  of 3 milliamps  halothane/70% n i t r o u s oxide) injection  was  a  reproducible  stimulation-evoked  of each experiment, the  The  e t al.,  (Steeves  1967;  observed,  l o c o m o t o r movements were i n i t i a t e d  stimulation current  After (EMG)  point  Hodos,  electrode  e v o k i n g l o c o m o t i o n was to the  and  stimulating with  for  linked)  60Hz;  10-170/iA.  the  (stimulus  parameters:  frequency =  lowering  until  current  were  cut  gelatinized slides  and  stained with Eosin/Cresyl  electrolytic sites, Hodos  were  V i o l e t dyes.  The l o c a t i o n o f  l e s i o n s , i n d i c a t i n g e f f e c t i v e locomotor identified  (1967) and Zweers  stimulation  a c c o r d i n g t o t h e a t l a s e s o f K a r t e n and (1971).  57  RESULTS  Medial  Longitudinal  Electrical fasciculus 5)  Fasciculus  (MLF)  s t i m u l a t i o n of the  along  a considerable  medial l o n g i t u d i n a l  rostrocaudal  e l i c i t e d v a r i e d locomotor patterns  geese,  1 Pekin  ranging  f r o m 30-160uA  bilateral flapping  stepping  any  sites.  in 3 birds  ( F i g . 6A),  combined  stepping  ( F i g . 6B)  intensity  or  stepping  was  to  electrical  taken  low  latter  was  during  frequency  MLF  of the  1986). i n the  while  the  stimulus  6).  6B)  elicited shown)  current one  seen  reticular  a l s o seen d u r i n g  locomotor p a t t e r n  58  showed  (not  intensity  s t i m u l a t i o n appeared to  1986) .  stimulation  of that  medullary  one  correlate  found i n only  reminiscent  As  and  in  (Figure  (Figure  & w i n g f l a p p i n g as  s t i m u l a t i o n of the e t al.,  flapping  animal  This pattern,  ramp i n c r e a s e s  threshold values  with  from 2 b i r d s  stimulation intensity  stimulated,  (Steeves  appear t o  records stepping  increased.  during  stimulation,  at  d i d not  o r i e n t a t i o n of the  stepping  seven b i r d s  and  and  wing f l a p p i n g alone  lateral  s t i m u l a t i o n of the  of the  formation  and  These v a r i e d p a t t e r n s  w h i c h gave way  force  included  stepping  alternating  intensities  patterns  Electromyographic  Electrical  Canada  92uA). The  rostrocaudal  alternating  (6  i n seven b i r d s  stimulation  4 &  (Figs.  (mean =  i n 3 animals  preparation. with  duck) a t t h r e s h o l d  extent  MRF above  increase  (Steeves  et  al.,  the  4.  Figure  pons and  Composite diagram o f c o r o n a l s e c t i o n s through mesencephalon i l l u s t r a t i n g  was  e v o k e d by  the  s e c t i o n s i s i n d i c a t e d by  each s e c t i o n Unfilled  electrical  discussed  A b b r e v i a t i o n s : AL  nucleus, LC  EM  part,  reticular  longitudinal  f o r m a t i o n , MV NIII  - o p t i c t e c t u m , PT reticular  Ru  - red nucleus,  nucleus, nigra,  SV  pars  - pretectal  nucleus,  formation,  Rpc  gray  nucleus, -  Hodos,  nucleus,  1967).  59  dorsal  mesencephalic NC  -  caudal  R - raphe nucleus,  RP  OT -  nucleus,  stratum,  VII  nucleus,  - t r i g e m i n a l nerve,  - oral part, pontine  - central  and  NV  - pontine  compacta, V - v e n t r i c l e , Karten  Edinger-Westphal  - motor t r i g e m i n a l n u c l e u s ,  - t r i g e m i n a l sensory  (Redrawn f r o m  MRF  by  brachium  IV - t r o c h l e a r  fasciculus,  nerve,  SGC  -  mesencephalic  - occulomotor  p a r v o c e l l u l a r p a r t , RPO  EW  are  aqueduct,  - decussation of the  - lateral  which  section.  - cerebral  - ectomammillary nucleus,  - medial  neostriatum,  pontine  DBC  AQ  of  (mm))].  i s indicated  corner of each  of  corner  stimulation sites  IP - i n t e r p e d u n c u l a r n u c l e u s ,  MLF  locomotion  (in millimeters  - ansa l e n t i c u l a r i s ,  - l o c u s c e r u l e u s , MLd  which  rostrocaudal extent  extent  i n the upper l e f t  - brachium conjunctivum,  conjunctivum,  The  P=posterior  represent e f f e c t i v e  levels  from  t h e numbers i n u p p e r l e f t  i n the t e x t . Rostrocaudal  stereotaxic  BC  stimulation.  [A=anterior,  circles  sites  the  TPc  reticular SP  nucleus,  - subpretectal  - substantia  - facial  nucleus.  A 0.75  A 3.00  60  Figure  5.  Coronal  sections  neuraxis  illustrating  elicited  by  the  caudal  the  MLF. B:  a  stimulated  illustrating  for  details.  reticular  ICo -  electrolytic  medial  raphe  lesion, medial  nerve,  part,  formation,  medial  dorsal  site  part,  in  the  nucleus,  (L)  the  Coronal an  the  stimulation See  site  Results  mesencephalic  Ipc  reticular  -  isthmal  lateral  nucleus,  an  mesencephalic MRF -  NV -  occulomotor  PrV -  in  through  tectum.  fasciculus,  part,  site  isthmal  marked by  formation,  (L)  illustrating  mesencephalic  dorsal  reticular  Omd -  nucleus,  Ru -  the  lateral  longitudinal  occulomotor  nucleus,  of  stimulation  MLd -  mesencephalic  trigeminal -  L -  C:  section  i n t e r c o l l i c u l a r nucleus,  part,  MLF -  trigeminal ventral  FRM -  site  locomotion-evoking  A b b r e v i a t i o n s : FRL -  parvocellular  nucleus,  a  be  through  stimulation  (MRF).  (L)  D: Coronal  i n t e r c o l l i c u l a r nucleus  formation,  formation,  (Ipc).  could  section  stimulation  site  the  mesencephalon  formation  locomotor  mesencephalon the  through the  of  locomotion  A: Coronal  r o s t r a l mesencephalon  nucleus  in  which  locomotion-evoking  reticular  parvocellular  (L)  from  locomotion-evoking  through the  electrically  a  section  mesencephalic  section  (L)  stimulation.  showing  Coronal  demonstrating medial  sites  electrical pons  through varying levels  nucleus,  principal  Omv -  sensory  R  RPgc  -  gigantocellular  red nucleus,  III  61  -  part,  occulomotor  pontine nerve  reticular  in  62  63  Figure  6.  activity  Electromyographic  e l i c i t e d by e l e c t r i c a l  longitudinal  fasciculus  r e p r e s e n t e d by EMG (LITC)  (EMG)  patterns  o f t h e MLF.  stimulation  showing l o c o m o t o r of the medial  (MLF). A: A l t e r n a t i n g from t h e r i g h t  iliotibialis cranialis  stimulation  records  stepping  (RITC)  m u s c l e s e l i c i t e d by  ITC i s t h e m a j o r  stimulation right  flapping  o f t h e MLF.  (RPECT) and l e f t  EMGs e v o k e d by  The t o p two (LPECT)  traces  and r i g h t  electrical and i s  Stepping  electrical are records  from t h e  p e c t o r a l i s muscles which are the  m a j o r w i n g d e p r e s s o r m u s c l e s . The b o t t o m from t h e l e f t  left  avian hip flexor  synonymous w i t h t h e mammalian s a r t o r i u s m u s c l e . B: t o g e t h e r w i t h wing  and  ITC f l e x o r  64  2 traces  muscles.  are records  LPECT H H — * — T — r ~ 4 — '  RITC  LITC  65  Medial Mesencephalic  Stimulation  Reticular  of the medial  Formation  (mMRF)  mesencephalic  ( F i g u r e 4) a t t h r e s h o l d c u r r e n t i n t e n s i t i e s 25-150uA  (mean = 78jiA) e l i c i t e d  (4 Canada g e e s e , patterns  seen  10 P e k i n d u c k s ) t h a t  i n response  displayed walking stimulation others, 7A)  were s i m i l a r  up t o 170uA  The  i n 4 other effects  maintaining several  from  tothe  o f t h e MLF. F i v e  a l o n e w i t h no w i n g p a r t i c i p a t i o n  intensities  F l y i n g behaviour  i n five  (e.g. F i g u r e  a l o n e was  animals.  o f changing  the frequency  and wing d e p r e s s o r  of stimulation  (PECT) EMGs from  the hindlimb one b i r d  walking  and f l y i n g  together at threshold  stimulation  intensity  (lOOuA).  Increasing the stimulus  both  flapping  leg  i n 10Hz increments  (2.5-0.83Hz)  and s t e p p i n g  a n d w i n g a r e shown f o r e a c h  Nucleus  decreased  Intercollicularis  flexor  which  demonstrated  t o 80Hz  while  c o n s t a n t were e x a m i n e d  a n i m a l s . F i g u r e 7B i l l u s t r a t e s  50Hz  birds  even a t  (maximum), w h i l e  other s t i m u l a t i o n parameters  from  formation  p a t t e r n s i n 14 a n i m a l s  to stimulation  at the threshold intensity.  (ITC)  ranging  s t e p p i n g and f l a p p i n g began s i m u l t a n e o u s l y  elicited  in  locomotor  reticular  frequency  t h e frequency o f  (2.3-1.3Hz)  ( o n l y one  frequency).  (ICo) a n d N u c l e u s  Isthmi,  p a r s p a r v o c e l l u l a r i s (Ipc)  Locomotion electrical  was e l i c i t e d  stimulation  i n n i n e Canada g e e s e by f o c a l  (threshold  intensity  range  25-100uA, mean  = 71uA) o f a r e g i o n i n c l o s e p r o x i m i t y t o t h e t e c t a l 66  F i g u r e 7.  EMG r e c o r d s showing locomotor a c t i v i t y produced by  e l e c t r i c a l s t i m u l a t i o n of the medial mesencephalic formation  (mMRF). A: S t e p p i n g t o g e t h e r w i t h wing f l a p p i n g EMGs  e l i c i t e d at a s t i m u l a t i o n threshold the l e f t left  reticular  (LITC) and r i g h t  (LPECT) and r i g h t  o f lOOuA. Records a r e from  (RITC) ITC muscles t o g e t h e r w i t h t h e  (RPECT) muscles. B: EMG r e c o r d s from t h e  same a n i m a l showing t h e e f f e c t s o f changing  stimulation  f r e q u e n c y on l o c o m o t i o n . The t r a c e s a r e p a i r e d t o i l l u s t r a t e t h e s i m u l t a n e o u s s t e p p i n g (LITC) and f l a p p i n g  (LPECT) b e h a v i o u r  e l i c i t e d a t a c o n s t a n t s t i m u l a t i o n i n t e n s i t y o f lOOuA and square wave p u l s e d u r a t i o n (2.0ms). The f r e q u e n c y o f s t i m u l a t i o n was v a r i e d from 50Hz i n t h e t o p p a i r t o 80Hz i n t h e bottom p a i r i n 10Hz  i n c r e m e n t s . The frequency o f s t e p p i n g d e c r e a s e d w i t h  i n c r e a s i n g frequency o f s t i m u l a t i o n - 1.7 s t e p s / s e c ,  (50Hz - 2.3 s t e p s / s e c , 60Hz  70Hz - 1.5 s t e p s / s e c ,  80Hz - 1.3 s t e p s / s e c ) .  The f r e q u e n c y o f wing f l a p p i n g a l s o d e c r e a s e d w i t h i n c r e a s i n g s t i m u l a t i o n frequency  (50Hz - 2.5 w i n g b e a t s / s e c , 60Hz - 2.0  w i n g b e a t s / s e c , 70Hz - 1.0 w i n g b e a t / s e c , 80Hz - 0.83 wingbeats/sec).  67  RPECT  LPECT  — •  4+4- t r  RITC i t  LITC 1 sec  68  B LPECT 50 Hz  LITC  LPECT 60 Hz  LITC  LPECT 70 Hz  LITC  LPECT 80 Hz  LITC  intercollicular  and  isthmal nuclei  ( F i g u r e s 4 & 5).  s t i m u l a t i o n produced stepping together animals.  An  example i l l u s t r a t i n g  wing locomotor p a t t e r n s  the  w i t h wing f l a p p i n g i n a l l  c o a c t i v a t i o n of leg  i s displayed i n Figure  70  Threshold  8.  and  Figure  8.  elicited nucleus  EMG by  of  right both  typical  electrical  left  locomotor  The  limb g i r d l e s  left  r e c o r d s were t a k e n  (LITC)  i n response  in this  region.  71  activity  intercollicular  (LPECT) p e c t o r a l i s m u s c l e s  (RITC) and  for sites  the  s t i m u l a t i o n of the  of the mid-brain.  (RPECT) and the  records i l l u s t r a t i n g  from  the  simultaneously  ITC m u s c l e s . to e l e c t r i c a l  The  right with  coactivation  s t i m u l a t i o n was  RPECT  LPECT  RITC  LITC i  1 1 sec  72  DISCUSSION  Previous locomotion reticular  s t u d i e s i n o u r l a b o r a t o r y have d e m o n s t r a t e d  c a n be e l i c i t e d formation nuclei  reticulospinal control and  region strip  (Steeves  e t al.,  e t al.,  of species  1988). Furthermore,  reticular  induced.  f i n d i n g s demonstrate  the t e c t a l  (MLR) a n d s u b t h a l a m i c  (Eidelberg,  1969) have 1981).  one r e g i o n i n t h e pons a n d  reticular  longitudinal formation  (ICo) a n d p a r v o c e l l u l a r  fasciculus  (MLF),  (mMRF) a n d t h e  isthmal  (Ipc) n u c l e i o f  ( K a r t e n a n d Hodos,  1967; C a r p e n t e r  midbrain.  In b i r d s , Sutin,  more  from w h i c h l o c o m o t i o n may be e l e c t r i c a l l y  mesencephalic  intercollicular  utilized  Equivalents of the  1966; O r l o v s k y ,  i n birds  These i n c l u d e t h e m e d i a l  the medial  region  (SLR) ( S h i k e t al.,  i n the midbrain  we have  t o examine s y s t e m a t i c a l l y  locomotor  not been p r e v i o u s l y i d e n t i f i e d present  o r modulate t h e  formation nuclei,  stimulation  mammalian m e s e n c e p h a l i c  .Our  activation of  1988; s e e C h a p t e r 1 ) .  brainstem  region  locomotor  ( M c C l e l l a n , 1986; J o r d a n ,  portions o f the avian brainstem.  locomotor  a  1986, 1 9 8 7 ) . The PLS  examine s t r u c t u r e s w h i c h may c o n t r o l  electrical  and ongoing  1986, 1987; Sholomenko  i n the sensorimotor  i n a variety  locomotor-related  rostral  (Steeves  to play a role  Noga e t al., To  and  t o the descending  f o r the i n i t i a t i o n  1987b; W e b s t e r a n d S t e e v e s ,  was d e s c r i b e d  locomotion  two  give rise  stimulation of  c o r r e s p o n d i n g t o t h e mammalian p o n t o b u l b a r  appears  1986;  that  pathways e s s e n t i a l  of locomotion  Steeves,  i n b i r d s by e l e c t r i c a l  that  as i n mammals  1983), t h e MLF d e s c r i b e s a f i b r e 73  tract  which  carries  a v a r i e t y of p r o j e c t i o n s . from the  level  medulla MLF  of the  (Karten  include:  reticular  and  1)  The  Hodos,  1967). P r o j e c t i o n s  d e s c e n d i n g axons t r a v e l l i n g  formation  s p i n a l cord,  nuclei  and  (PRF)  to the  1984),  the  medullary  and  4)  IV  3)  olive  interstitial  ( C a r p e n t e r and  vestibulospinal reticular  I I I . In  addition,  (unspecified Several  the  MLF  Fibres and  project  and  thus could  associated the  to  (Rye  activate  be  et  (PPN)  al.,  locomotion  stimulation.  v i a the al,  et  elicits  head or  MLF  locomotor  facilitates  to the  VI,  the via  the  travelling  in  mechanisms stimulation  of  manner.  and  spinal  MLF cord  responses  However, d i r e c t s t i m u l a t i o n  S i m i l a r l y , although  (Garcia-Rill only  only  et  1983)  c a r r i e d i n the  formation  v e s t i b u l a r n u c l e u s does n o t  projections  Sutin,  also project  v e s t i b u l a r n u c l e i are  f o r the  cat.  Skinner  in a non-specific  responsible  1972a) b u t  vestibular  1983;  i n locomotor c o n t r o l  reticular  decerebrate  Sutin,  (INC)  1987).  medullary  w i t h MLF  lateral  (Orlovsky,  the  descending  r e s u l t s . Thus, e l e c t r i c a l  a r i s i n g from the  cord,  nucleus of C a j a l  above d e s c e n d i n g p r o j e c t i o n s  s u b s e r v e our  f i b r e s may  spinal  the  pontine  f i b r e s from c r a n i a l n e r v e n u c l e i  have b e e n i m p l i c a t e d  w h i c h may these  of the  caudal  some f i b r e s w h i c h i m p i n g e on  origin)  is  which t r a v e r s e  ( C a r p e n t e r and  pedunculopontine tegmental nucleus MLF  MLF  f i b e r s which send c o l l a t e r a l s t o  formation  visual internuclear  and  of the  from the  m e d u l l a and  P r o b s t ' s t r a c t , m e d i a l and  inferior  al.,  extent  Edinger-Westphal nucleus t o the  2 ) d e s c e n d i n g axons f r o m t h e to  rostrocaudal  activate  conjugate v e r t i c a l  the  sends d i r e c t  motor a s s o c i a t e d  1983a), e l e c t r i c a l  locomotion  extensor tone i n  INC  of  Probst's  stimulation and  of the  rotatory  eye  Tract INC  movements  (Skinner  reticular  formation  of postural  al.,  et  tonus  1984). A c t i v a t i o n o f  f i b r e s have b e e n i m p l i c a t e d  i n the  cat  (Mori  f i b r e s have b e e n d e m o n s t r a t e d t o reticular et  al.,  formation  1987,  could  also  and  account .for the  locomotion. E l e c t r i c a l neurons of the  PPN,  form a p o r t i o n  of the  (Garcia-Rill eliciting  Steeves,  mesencephalic 1986)  could  l o c o m o t i o n t h r o u g h MLF  However, w h i l e e l e c t r i c a l projections  l o c o m o t i o n evoked from the  which w i l l that  be  locomotion r e s u l t e d  MLF  the  from the  responsible  determined i n b i r d s ,  to  electrically  on on  1981;  cells  Taccogna et  axonal in  from  injection  studies indicate  stimulation-induced  o f en  passant  of c e l l s  fibres in this to  al.,  a region  be  neurons which s t a i n  have b e e n i d e n t i f i e d  appear t o p r o j e c t  identified  for  f o r l o c o m o t i o n have y e t  locomotion-evoking  midbrain,  to  (MLR)  ( C h a p t e r s 3 & 5)  serotonin-containing  to the  of the  and  have some r o l e  connections  for acetylcholinesterase  pretectalis  of the  results  stimulation  be  serotoninergic  responsible  r e s u l t s o f MLF  region  Parent,  (Steeves  stimulation.  region,  neuroanatomical  (Dube and  a l s o be  stimulation  alone. While the  close proximity  in birds  locomotor region  subsequently discussed  i t i s u n l i k e l y that  positively  medullary  stimulation  (or a g o n i s t s / a n t a g o n i s t s )  w h i c h may  These  axons t e r m i n a t i n g  a r i s i n g f r o m t h e s e n u c l e i may  neurotransmitter  1982).  a mesencephalic nucleus which appears  al.,  et  of  control.  i n preparation)  e f f e c t s o f MLF  stimulation  the  structures 1988,  i n the  1978,  i m p i n g e on  spinal cord  W e b s t e r and  al.,  et  pontine  stimulation  sites  in preparation). to the  in  These  nucleus  lying in close  locomotor s i t e s which w i l l  proximity be  discussed the  below  (Reiner  GABAergic a g o n i s t  e t al.,  1982). In t h e r a t ,  muscimol  raphe n u c l e i i n c r e a s e s  ibotenic  acid lesion of c e l l  produced h y p e r a c t i v i t y  bodies within  1987).  t h e median  t h i s region  by e l e c t r i c a l  stimulation  Also,  raphe 1983).  i n locomotor  i n t h e i n t a c t mammal. W h i l e t h e o b s e r v e d  behaviour e l i c i t e d may  ( P a r i s and L o r e n s ,  implicate  o r median  w h i c h i s b l o c k e d by  i n t h e r a t (Asin and F i b i g e r ,  These r e s u l t s , t h e r e f o r e , processes  into either the dorsal  locomotor a c t i v i t y  pre-treatment with b i c u c u l l i n e  i n j e c t i o n of  locomotor  o f t h e MLF i n b i r d s  r e s u l t from a c t i v a t i o n o f neurons i n t h i s r e g i o n ,  the  mechanism a n d n e u r o a n a t o m i c a l p a t h w a y s t h r o u g h w h i c h t h e locomotion  i s e v o k e d r e m a i n s t o be d e t e r m i n e d .  Electrical  stimulation  mesencephalic r e t i c u l a r locomotion effective  o f a second region,  formation  (mMRF),  also  the medial elicited  i n d e c e r e b r a t e b i r d s . The r o s t r o c a u d a l stimulation  sites  (from c a u d a l  extent  red nucleus to r o s t r a l  pons) i n d i c a t e s t h e d i f f u s e n a t u r e o f t h i s l o c o m o t o r In b i r d s , shown t h a t (layers  a n t e r o g r a d e and r e t r o g r a d e  1984). In t u r n , innervation  deep t e c t a l  equivalent  are  tracing studies  (Hunt e t al., layers  from t h e l a t e r a l  nucleus which i t s e l f  Bilateral  region.  t h e mMRF has r e c i p r o c a l c o n n e c t i o n s w i t h deep  8-13) o f t h e t e c t u m  receives  receive  patients,  layers  the bulk of t h e i r (SpL),  a relay  t h e major o u t f l o w o f t h e a v i a n ganglia  (Reiner  o f SpL r e s u l t s i n d e f i c i t s  s i m i l a r , as i n monkeys w i t h p a l l i d a l  Parkinsonian  have  1977; Hunt and B r e c h a ,  s p i r i f o r m nucleus  o f t h e mammalian b a s a l destruction  of the  i n birds  l e s i o n s and  t o those seen f o l l o w i n g  o u t f l o w pathway f r o m t h e mammalian b a s a l  e t al.,  1984). that  also i n  d i s r u p t i o n of the  ganglia  (Bugbee,  197 9,  c f Reiner  e t al., 1 9 8 2 ) . Thus, t h i s  controlling  the  initiation  which c o o r d i n a t e Reiner  e t al, 1982;  The spinal  o f o n g o i n g o r i m p e n d i n g movements  b i r d ' s p o s i t i o n i n space Reiner  cord  and t o the  reticular  preparation). outflow  This  loop  data  formation  identified  circuit  from the b a s a l  the  avian  1984;  of this  which have been  (Garcia-Rill et  Rye e t al., 1 9 8 8 ) . avian  region t o the  o f mammals a w a i t s  i n the  preparation  through e l e c t r i c a l  deep t e c t a l  regions  increased  immunohistochemical and  low d e c e r e b r a t e  bird  stimulation of a third  i n c l u d i n g the  p a r v o c e l l u l a r isthmal  connections  structures  information.  L o c o m o t i o n was e l i c i t e d  and  those  locomotor regions  locomotor regions  subtype  a portion of  a f f e r e n t and e f f e r e n t pathways o f  a n d mammalian n e u r o a n a t o m i c a l ,  receptor  medial  c o n s t r a i n t s o f the a v a i l a b l e  a v i a n mMRF c o n n e c t i o n s ,  f u r t h e r comparison  cervical  o f motor performance i n b i r d s  above r e s e m b l e t h e  mesencephalic  o f the  ganglia to hindbrain  1983a; S t e e v e s a n d J o r d a n ,  However,  high  may, t h e r e f o r e , p r o v i d e  t h e mammalian m e s e n c e p h a l i c al.,  1979, c f  (Webster a n d S t e e v e s , i n  e t al., 1 9 8 4 ) . W i t h i n  concerning  both t o the  g i g a n t o c e l l u l a r region  w h i c h u n d e r l i e s some a s p e c t s (Reiner  (Bugbee,  e t a l . , 1984).  mMRF p r o j e c t s i p s i l a t e r a l l y  medullary  the  the  pathway may have a r o l e i n  intercollicular  nucleus  through which these  site, the  n u c l e u s (ICo)  ( I p c ) . The n e u r o a n a t o m i c a l  regions  elicit  locomotor  b e h a v i o u r a r e p r e s e n t l y unknown. However, some p a t h w a y s w h i c h may  u n d e r l i e o u r r e s u l t s have b e e n ICo  1976;  receives  input  from the  Webster and Steeves,  identified.  s p i n a l cord  i n preparation), 77  (Hunt a n d K u n z l e , deep t e c t a l  layers  (Hunt e t al., from the direct  1977;  c u n e a t e and  tract  gigantocellular medullary  gracile  cervical  mesencephalic reticular  MLR  Jordan,  1986;  On  the  ventrally  circuit  through  reminiscent  ( R e i n e r et  of those  regions  structures  found  (MLR)  al.,  e t al.,  and  acetylcholinesterase cholinergic 2&3)  input  the  deep t e c t a l  the  turtle  and  ( T a c c o g n a e t al.,  (AChE)  from the  (Hunt e t al., layers frog,  e t al.  (1982)  cuneiform the  1984;  s t i m u l a t i o n of the i n our  which s t a i n s p o s i t i v e l y  (CHAT)  1983a;  Jordan,  l o c a t e d Ipc a l s o evoked locomotion  acetyltransferase  to  1988).  o t h e r hand, e l e c t r i c a l  nucleus  These  mammalian  o f t h e mammalian  Steeves  a  basal  i n mammals, i s b e l i e v e d t o be  1966;  Noga e t al.,  be  which p r o j e c t d i r e c t l y  1988). Indeed, Cabot  ( S h i k e t al.,  may  1984).  f o r the  (Garcia-Rill  to those  ICo  and  avian  1982;  high  1 9 8 2 ) . Thus,  which the  central  Karten,  ipsilateral  Karten,  control  connections  a tectal  (layers  ipsilateral  to locomotion-related nuclei  a p o r t i o n o f which,  lateral  contralateral  ( R e i n e r and and  input  descending  and  (Rgc),  (Cnv)  afferent  1987). I t sends  rostral  ipsi-  formation  Noga e t al.,  compare t h e s e  (TTD),  ( R e i n e r and  locomotor  1986;  nucleus,  cord  formation  (Wild,  i n preparation)  locomotor  are  body-related  nuclei  ventral part  output  affect  connections  Jordan,  reticular  connections  of the  and  ipsilateral  nucleus  Steeves,  spinal  maintains  ganglia  and  nucleus,  W e b s t e r and  Ipc,  1987)  p r o j e c t i o n s t o the  trigeminal  relay  Wild,  (Hunt e t al., superficial 1977)  (layers  and 8-13)  ChAT-positive  78  more  preparation.  f o r both  choline  i n preparation) 1977)  (visual)  and  receives tectal  layers  also receives input ( R e i n e r e t al,,  isthmal nucleus  from  1982).  neurons  In have  been demonstrated (Desan e t al.,  t o send  a cholinergic projection  1984), w h i l e  have b e e n l o c a l i z e d  i n the  birds,  based  on u p t a k e  of  lateral  Similarly,  and  that  3  GABAergic e f f e r e n t s al.,  1977),  homogeneous, may  be  labelling  studies,  superficial  (Hunt  or sensorimotor preparation).  (TTD)  circuit,  the  layer  1982).  3  layers  appear t o  reticular  i n decerebrate birds,  output  Ipc t o  and (Hunt  et  1982). In r e t r o g r a d e  (Webster and  i s evoked i n d i r e c t l y  In  glycinergic  Therefore, while e l e c t r i c a l  evokes locomotion behaviour  nuclei  1987)].  histologically  I p c does n o t  innervate motor-related brainstem  be  with respect to  e t al.,  however,  to  [ H ] g l y c i n e and  tectal  Ipc, w h i l e  neurons  transport studies,  e t al.,  studies using  heterogeneous  neurotransmitter type  (Hunt  Ipc neurons p r o j e c t  that  Reiner,  HRP  tectum  [thought  been p o s t u l a t e d from  caudal tectum  to the  indicating  ( V i n c e n t and  3  r a d i o a c t i v e uptake  [ H]GABA s u g g e s t  nucleus  [ H ] c h o l i n e and  a c h o l i n e r g i c p r o j e c t i o n has 2d o f t h e  cat, ChAT-positive  to the parabigeminal  t h e mammalian e q u i v a l e n t o f I p c  to the  v i a an  o f which remains  directly  formation  Steeves,  Cnv)  in  stimulation  i t appears  of  that  Ipc t o t e c t a l t o be  (Rgc,  Ipc the  neuronal  determined.  CONCLUSIONS  The pontine  results  of t h i s  and m e s e n c e p h a l i c  investigation analogous  study  demonstrate  locomotor  regions i n birds.  i s r e q u i r e d t o determine  t o t h e more r o s t r a l  higher vertebrate species  the presence  locomotor  ( f o r review,  whether t h e s e regions  (MLR  of  Further regions  are  o r SLR)  of  see Noga e t al.,  1988).  One l o c o m o t o r  site,  located  close t o or w i t h i n the  intercollicular  nucleus  possess  of the hodological c h a r a c t e r i s t i c s  several  mammalian MLR. determine mammalian  of the t e c t a l  midbrain,  However, c o n s i d e r a b l y more s t u d y  whether t h i s  site  appears  to  of the  i s required to  i s an a v i a n e q u i v a l e n t o f t h e  MLR.  S t u d i e s w h i c h combine e l e c t r i c a l stimulation  of these  locomotor  with  regions w i l l  neurochemical help to  determine  w h e t h e r n e u r o n a l p o p u l a t i o n s o r axons o f p a s s a g e a r e b e i n g stimulated.  Some s t u d i e s u s i n g t h i s  a l r e a d y been u n d e r t a k e n neuroanatomical tracers  tract  experimental paradigm  (see C h a p t e r s  tracing  2-4). Furthermore,  using anterograde  and r e t r o g r a d e  combined w i t h r e c e p t o r a u t o r a d i o g r a p h i c b i n d i n g s t u d i e s  of l o c o m o t o r - e f f e c t i n g r a d i o a c t i v e neurochemicals determine involved  have  the neuronal i n locomotor  subpopulations control.  80  from  these  would h e l p t o regions  CHAPTER 3  CHARACTERIZATION OF AVIAN MID- AND HINDBRAIN SITES THAT PRODUCE LOCOMOTION WITH LOCAL INTRACEREBRAL INFUSION OF NEUROTRANSMITTER AGONISTS AND ( I ) : ACETYLCHOLINE  81  ANTAGONISTS  INTRODUCTION  The  initiation  locomotion of both  and ongoing  o f normal v e r t e b r a t e  d e p e n d upon t h e p r o d u c t i o n , i n t e g r a t i o n  centrally  interacting  and p e r i p h e r a l l y  a t many l e v e l s  In o r d e r t o u n d e r s t a n d level  control  generated information  of the central  the possible  nervous  approach  h a s b e e n t o examine t h e s y s t e m  portions  o f t h e CNS i n r e d u c e d  Zangger,  1979; G r i l l n e r  by u t i l i z i n g  preparations  and Kashin,  of locomotion  (Garcia-Rill, 1975), et  only  ( G r i l l n e r and  1 9 7 6 ) . One example w h i c h h a s electrically  c a t p r e p a r a t i o n p i o n e e r e d by S h i k a n d h i s c o - w o r k e r s  ( S h i k e t al., 1 9 6 6 ) . T h i s t y p e study  (CNS).  l o c o m o t i o n , one  yielded valuable information i s the decerebrate  the  system  c o n t r i b u t i o n made by e a c h  o f t h e complex n e t w o r k w h i c h c o n t r o l s  stimulated  and t r a n s f e r  o f p r e p a r a t i o n has been used f o r  i n a variety  1983, 1986; J o r d a n ,  including birds  of vertebrate species  1986; f o r r e v i e w  (Sholomenko a n d S t e e v e s ,  see G r i l l n e r ,  1987a;  Steeves  al., 1 9 8 7 ) . My s t u d i e s w i t h d e c e r e b r a t e g e e s e a n d d u c k s have shown t h a t  electrical medulla,  stimulation  i n c l u d i n g the pontobulbar  mesencephalic medullary  reticular  reticular  locomotion to those  o f r e g i o n s i n t h e m e s e n c e p h a l o n , pons a n d  i n a variety  s t r i p (PLS)  (MRF) a n d p o n t i n e a n d  formation, e l i c i t  from w a l k i n g t o f l y i n g .  found  (for review  formation  locomotor  a l l patterns of  These f i n d i n g s ,  avian  complementary  o f b o t h h i g h e r and lower v e r t e b r a t e s  s e e M c C l e l l a n , 1986),  t h e m i d - a n d h i n d b r a i n as p l a y i n g control.  82  strongly  implicate  a major r o l e  nuclei of  i n locomotor  Although stimulation review  locomotion  i n well circumscribed  see G r i l l n e r ,  limited  c a n be e l i c i t e d  information  the behaviour.  1975), t h i s concerning  Electrical  by  regions type  electrical  of the brainstem (for  of stimulation gives  the neural  structures underlying  s t i m u l a t i o n a c t i v a t e s a l l neuronal  elements i n c l u d i n g d i s t a n t l y  originating  axons o f p a s s a g e (en  p a s s a n t ) w h i c h may t r a v e r s e t h e p o i n t o f s t i m u l a t i o n et  al., 1982; G a r c i a - R i l l  1 9 8 8 ) . To c i r c u m v e n t physiological utilized  this  activation  neurotransmitters, (neurochemicals) electrically  not,  agonists  receptors  (Goodchild  or blockade,  (Goodchild  region yields  two t y p e s  of information. F i r s t ,  i t aids i n the d e f i n i t i o n  Correlation of this  neuroanatomical  The on:  of receptors  believed to give r i s e  powerful  an e l e c t r i c a l l y  choice  previous  have  by  defined  locomotor  i t differentiates  and en p a s s a n t  fibers.  o f receptor types  present  on  t o pathways i n v o l v e d i n l o c o m o t o r type  of finding  with  i n f o r m a t i o n makes neurochemical  paradigm  cell  e t a l . , 1982).  o f locomotor behaviour  into  between t h e a c t i v a t i o n  when  e t al., 1 9 8 2 ) . R e c e p t o r s  injection  control.  and a n t a g o n i s t s  s i t u a t e d on d e n d r i t e s ,  on axons  then,  we  are thought t o  neurochemical  cells  regions,  s i t e s which produce locomotion  however, b e e n l o c a l i z e d  Second,  mimic t h e  injecting  s t i m u l a t e d . T h e s e neurochemicals  and t e r m i n a l s  Activation  related  s t i m u l a t i o n by  activate neurotransmitter bodies  p r o b l e m a n d t o more c l o s e l y  or neurotransmitter  into  (Goodchild  e t a l . , 1985, 1987; Noga e t a l . ,  of locomotion  pharmacological  only  f o r t h e study  o f locomotor  of neurochemicals  control.  used i n t h i s  i n v e s t i g a t i o n s using chemical 83  stimulation a  study  was b a s e d  stimulation  (Garcia-Rill al., 291);  e t al.,  1985, 1987; Noga e t al., e t al.,  1985 ; B r u d z y n s k i neuroanatomical  immunocytochemical  1988; E l d r i d g e e t  1986, 1988 (see A p p e n d i x  information;  localization  and a u t o r a d i o g r a p h i c and  of receptors  types and  transmitter profiles  for n u c l e i i n the regions  to e l i c i t  when e l e c t r i c a l l y  locomotion  neurochemicals u t i l i z e d effects  of c h o l i n e r g i c agonist  previously  defined  have b e e n f o u n d , this  study  detailed left  avian  was d e s i g n e d  examine t h e l o c o m o t o r  and a n t a g o n i s t  locomotor regions.  injection  Because s i x  o f these  into regions  extensive,  regions,  with  characterization of individual  results  demonstrate t h a t neuroactive  at s t i m u l a t i n g or blocking avian  previously defined using  (Steeves  e t al.,  more  regions  following injection  locomotion  the corresponding  agonists/antagonists  t o onset  hindbrain  were  locomotor p a t t e r n s i n  electrical  decreased  stimulation or the threshold  i n a variety of  o f c h o l i n e r g i c a g o n i s t s . The or e l e c t r i c a l  antagonist.  threshold  appeared t o possess  and l o n g e v i t y o f a c t i o n  individual with  times  be compared t o r e c e n t  a view t o d e f i n i n g mid- and  p a t h w a y s i n v o l v e d i n motor c o n t r o l .  84  varying  (see T a b l e 1 ) .  i n the bird w i l l  i n t h e c a t and r a t , w i t h  increased  The e f f e c t i v e  f o r a c t i v a t i o n o r blockade,  These r e s u l t s findings  locomotion  c o u l d be b l o c k e d  characteristics  only  chemicals  1 9 8 7 ) . L o c o m o t i o n was e l i c i t e d  for electrically-induced  with  chapter  as a s u r v e y  shown  s t i m u l a t e d . The  a n d t h e number o f n e u r o t r a n s m i t t e r s  neurochemical  effective  sites  previously  to future investigations. Our  sites  i n this  I , pp.  MATERIALS AND METHODS  Surgery  The  surgical  and d e c e r e b r a t i o n  electromyographic and in  recordings  wing d e p r e s s o r  muscles  paralyzed  with  (PECT) have b e e n p r e v i o u s l y  ITC  described  (0.025ml/kg) were r e c o r d e d  f o r EMGs b u t a t h i g h e r  the treadmill o f f .  Stimulation  Both e l e c t r i c a l regions  and c h e m i c a l  within the brainstem  stimulation of localized  were u s e d t o e l i c i t  locomotion  p r e p a r a t i o n . A monopolar s t i m u l a t i n g e l e c t r o d e , inserting  0.0762mm s t a i n l e s s  s t e e l wire  barrel micropipette stereotaxically (Steeves  (exposed t i p l e n g t h =  p r e v i o u s l y shown t o e l i c i t  e t a l . , 1987; Sholomenko a n d S t e e v e s ,  barrels of the micropipette  neurochemicals microsyringe  three  ( t o t a l t i p d i a m e t e r = 0.1mm), was p o s i t i o n e d  into sites  neurotransmitter  from  constructed  0.1mm, impedance = 60-70kQ) down one b a r r e l o f a p u l l e d  two  using  on p e r i p h e r a l n e r v e s t o  t h e same e q u i p m e n t u s e d  (10,000x) a n d w i t h  Brain  (ENGs) f r o m v e n t i l a t e d a n i m a l s  hook e l e c t r o d e s p l a c e d  a n d PECT w i t h  gain  records  d-tubocurarine  bipolar platinum  by  f r o m t h e l e g f l e x o r m u s c l e s (ITC)  C h a p t e r 2. Electroneurographic  the  procedures and  agonists,  were f i l l e d  antagonists  1 9 8 7 a ) . The o t h e r  with  or saline.  were d e l i v e r e d t o t h e m i c r o p i p e t t e  (Hamilton) v i a f l e x i b l e  85  vinyl  locomotion  tubing.  These from a Constant  current  stimulation t r i a l s  were u n d e r t a k e n w i t h s q u a r e wave p u l s e current  strength  M o d e l S88/ G r a s s Model CCU1A)  the following stimulation  duration  - 1.0-2.Oms, p u l s e  trials  the electrode  into the brainstem while  intensity  observed,  t h e s t i m u l a t i o n was t u r n e d  ranging  then reduced t o zero.  current  intensity  o f f . The c u r r e n t  increased  electrode  t o t h e p o i n t where c o o r d i n a t e d t h e lowest  1 9 8 7 ) . Once o p t i m a l  until  Table  on a n d t h e  t h r e s h o l d was  lowering  the electrode  l o c o m o t o r movements were  stimulation current  (Steeves  e l e c t r o d e p o s i t i o n was e s t a b l i s h e d ,  or antagonists  1 ) . The i n j e c t i o n  volume o f 1. Oul  intensity  t i p p o s i t i o n f o r evoking  s t i m u l a t i o n was a t t e m p t e d b y i n j e c t i o n agonists  with  f r o m 50-100uA. When l o c o m o t i o n was  l o c o m o t i o n was t h e n e s t a b l i s h e d b y s l o w l y  with  - 60Hz,  stimulating  The s t i m u l a t o r was t u r n e d  was s l o w l y  r e a c h e d . The o p t i m a l  initiated  frequency  were u n d e r t a k e n b y i n c r e m e n t a l l y  a current  was  parameters:  - 25-170fiA.  Stimulation lowering  (Grass  al.,  et  chemical  of neurotransmitter  (agonist/antagonist)  i n t o t h e s i t e (see  r a t e was 0 . 2 u l / m i n u t e t o a maximum  f o r any one  neurochemical  solution  (pH7.2-7.4)  (unless otherwise stated, l u l volumes were injected). The concentration  o f each s o l u t i o n v a r i e d , with  concentrations et  al.,  b a s e d on t h o s e u s e d b y o t h e r  1988; G a r c i a - R i l l  Brudzynski  e t al.,  experiments,  investigators  1985; E l d r i d g e  e t al.,  (Noga  1985;  1986, 1 9 8 8 ) . O v e r t h e c o u r s e o f many .  an a t t e m p t was made t o s y s t e m a t i c a l l y t i t r a t e t h e  concentration suprathreshold locomotion  e t al.,  initial  o f each a g o n i s t / a n t a g o n i s t concentration  (see T a b l e  t o f i n d t h e lowest  t h a t would s t i l l  elicit  1 ) . To examine t h e e f f i c a c y  86  or block  o f each  neurochemical  and i t s time course,  the following  were p e r f o r m e d t o d e t e r m i n e t h e e f f e c t s injection  upon l o c o m o t i o n ;  producing  neurochemical  antagonist  1)  and v i s e v e r s a  2)  of agonist/antagonist  injection  upon e l e c t r i c a l  the  After  either  i n t h e same s i t e  identification cathodal  with  and/or i n  contralaterally.  s t i m u l a t i o n and  stimulation/injectionsite  direct  t o examine t h e e f f e c t o f  r e c o r d i n g t h e locomotor a c t i v i t y  following e l e c t r i c a l the  stimulation following  s t i m u l a t i o n t h r e s h o l d a n d 3)  o f each i n j e c t i o n  homologous s i t e  locomotion  of i t s corresponding  electrical  injection  replication  of agonist/antagonist  counteracting a  by i n j e c t i o n  manipulations  injection,  l e s i o n made b y p a s s i n g a  of 3 milliamps  H i s t o l o g i c a l procedures were t h e same a s t h o s e  neurochemical  was marked f o r n e u r o a n a t o m i c a l  an e l e c t r o l y t i c  current  (EMGs a n d / o r ENGs)  f o r 5 seconds.  and s t i m u l a t i o n s i t e  d e s c r i b e d i n Chapter  87  2.  identification  RESULTS $>  Acetylcholine Agonists  A variety  and A n t a g o n i s t s  of cholinergic muscarinic  (ACtm) a n d n i c o t i n i c  (AChN) r e c e p t o r a g o n i s t s a n d a n t a g o n i s t s were i n f u s e d i n t o in  the brainstem  subtypes  i n an a t t e m p t  a c t i v a t e d . The  agonist;  to delineate the receptor  neurochemicals  AChM+N a g o n i s t , p i l o c a r p i n e , atropine sulfate,  u s e d were: c a r b a c h o l , an  an AChM a g o n i s t ; n i c o t i n e , an AChM a n t a g o n i s t  an AChM a n t a g o n i s t . N e u r o c h e m i c a l  injection  effective  course  in  Table  c o n c e n t r a t i o n s and time 1 (also  The  see Appendix  sites,  the pontobulbar within  tract  into  nucleus  reticular  formation,  reticular  nucleus  included lies  a p p o s i t i o n t o t h e descending  (TTD)),  the dorsal part of the  nucleus  reticular  formation, the  (Cnv) i n t h e m e d u l l a r y  the g i g a n t o c e l l u l a r part of the pontine  (RPgc),  (MRF) a n d t h e m e d i a l  was e l i c i t e d by  (PLS) (a r e g i o n w h i c h  (Cnd) i n t h e m e d u l l a r y  ventral part of the central  s i x regions  9 & 1 0 ) . These r e g i o n s  strip  and nucleus  are l i s t e d  I) a n d d e s c r i b e d i n t h e t e x t .  or i n close ventromedial  trigeminal central  locomotor  lowest  of activity  o f t h e mid- and h i n d b r a i n from which l o c o m o t i o n stimulation (Figs.  an AChN  and; scopolamine,  a g o n i s t s o r a n t a g o n i s t s were i n j e c t e d  electrical  sites  t h e mesencephalic  longitudinal  fasciculus  reticular  formation  (MLF) o f t h e p o n s .  A composite diagram o f t h e e l e c t r i c a l s t i m u l a t i o n / n e u r o c h e i n i c a l injection indicating  sites  i s shown i n F i g u r e  effective  sites  9 and examples o f l e s i o n s  a r e shown i n F i g u r e 10.  88  TABLE 1 Acetylcholine Agonists and Antagonists Animal  Sit*  Concentration! Injected  Lowed Effect ive Concentration  Volume  Rate  Carbachol 7.2-7.4 '• Scopolamine M Nicotine '• Atropine •• Pilocarpine " Carbachol Scopolamine Atropine  25mM-100mM 2SmM 2SmM 2SmM SOmM 11mM-100mM 25mM 30mM  2SmM none none 25mM none 11mM none SOmM  I.Oul  0.2ul/min  2.2-12  7-45  •• ••  — — 6  — — 25  " "  7 3.3-6  "  — <5  8 33  7.2-7.4 Carbachol Scopolamine " Nicotine Atropine " Pilocarpine  27-100mM 25mM 100mM 3-S0mM 60mM  27mM none none 20mM none  RP  Carbachol  64 mM  none  MRF  Carbachol  ••  100mM  100mM (RT)  MLF  Carbachol  ••  27-100mM  27mM  decerebrate TTD bird  Cnd  Cnv  Chemical  PH  ABBREVIATIONS: Cnd Cnv MLF MRF RP RT TTD  — — — — — — —  dorsal part, medullary central nucleus ventral part, medullary oentral nucleus medial longitudinal faaoiculus mesencephalic reticular formation pontine reticular nucleus reduced threshold for electrically stimulated locomotion descending trigeminal tract and nucleus  89  •'  " "  — >26  ••  2.2-6  7-46  — — 21-40  "  — — >7.6 — — — 9-10  23-40  " "  ••  "  Time C o u r t * (min) Latency Period  •• ••  -  —  45  Figure  9.  antagonist  Composite diagram  neurochemical  sections through in  upper l e f t  mm)]  brainstem  cholinergic  injection  various levels  c o r n e r o f each  illustrates  of  The d i a g r a m  of the avian neuraxis  level,  t h e locomotor  sites.  a g o n i s t and  A=anterior,  effects  of coronal [numbers  P=posterior ( i n  neurochemical  o f each  r e g i o n s f r o m w h i c h l o c o m o t i o n was f i r s t  e l i c i t e d by  electrical  s t i m u l a t i o n . Where a t r o p i n e i s shown a s f i l l e d  triangles,  i t s effect  Key  was t o b l o c k  A b b r e v i a t i o n s : ATRO - a t r o p i n e  (square),  NICO - n i c o t i n e  (hexagon), (except  (circle),  SCOP - s c o p o l a m i n e  f o r atropine),  in  locomotion. (triangle),  CARB - c a r b a c h o l  PILO - p i l o c a r p i n e  (diamond);  TH - d e c r e a s e d  LOCO - l o c o m o t i o n  electrical threshold  intensity  f o rlocomotion,  ^TH - i n c r e a s e d e l e c t r i c a l t h r e s h o l d  intensity  f o rlocomotion,  NR - no r e s p o n s e .  A b b r e v i a t i o n s : AL - a n s a  lenticularis,  central  c a n a l , Cnd - c e n t r a l  central  nucleus medulla,  nucleus,  10 - i n f e r i o r  longitudinal nucleus, nerve,  N V - trigeminal  formation,  EM -  MRF - m e s e n c e p h a l i c  R - raphe  ectomammillary  reticular  tract  motor n u c l e u s  formation  occulomotor  N X I I - h y p o g l o s s a l nerve,  nucleus,  RP - n u c l e u s p o n t i n e  SSP - s u p r a s p i n a l n u c l e u s ,  SV - t r i g e m i n a l  descending  nerve,  Cnv -  n u c l e u s , MLF - m e d i a l  Rpc - p o n t i n e p a r v o c e l l u l a r  nucleus,  nucleus,  ventral part,  CC -  dorsal part,  MV - t r i g e m i n a l m o t o r n u c l e u s , N I I I -  o p t i c tectum,  red  nucleus medulla,  olivary  fasciculus,  AQ - a q u e d u c t ,  reticular  and n u c l e u s , V I I - f a c i a l  90  reticular  nucleus,  Ru -  ST - s u b t r i g e m i n a l  sensory nucleus,  vagus.  OT -  TTD - t r i g e m i n a l nucleus,  X - dorsal  A 3.75  LOCO JTH 1TH \H PILO  •  ©  ©  O  SCOP  •  •  •  o  NICO  •  ©  ©  O  CARS  •  B  B  •  AM)  A  Iff  AAA  P3.75  P 4.50  91  Figure  10 C o r o n a l  illustrating  electrical  which e l i c i t e d section  sections  Coronal  stimulation/injection near  region, dorsal  site  the caudal site  i n the pontine  nucleus,  o l i v a r y nucleus,  stimulation/injection fasciculus, - pontine  - descending  medulla  r e t i c u l a r formation  nucleus,  found  i n each  canal,  Cnd -  Cnv - v e n t r a l  IM - i n t e r m e d i a t e n u c l e u s ,  part, 10 -  L - l e s i o n made a t  site,  MLF - m e d i a l  NVIII - g l o s s o p h a r y n g e a l r e t i c u l a r formation, trigeminal  site  (L) i n Cnv. D:  (R). F o r t h e e f f e c t s  c e n t r a l medullary  medullary  section  t h e pons i l l u s t r a t i n g a  t h e raphe nucleus  part,  inferior  nucleus  through  see R e s u l t s . A b b r e v i a t i o n s : c c - c e n t r a l  central  RP  b i r d . A: C o r o n a l  showing a s t i m u l a t i o n / i n j e c t i o n  section  through  sites  showing a  a stimulation/injection  section  brainstem  (L) i n TTD. B: C o r o n a l  the caudal medulla  demonstrating  (RP)  i n the decerebrate  site  (L) i n Cnd. C: C o r o n a l  the avian  neurochemical s t i m u l a t i o n  the caudal medulla  stimulation/injection through  and  locomotion  through  through  longitudinal  nerve,  92  nucleus,  SSP - s u p r a s p i n a l n u c l e u s , TTD  t r a c t and n u c l e u s ,  o f t h e vagus.  R - raphe  X - dorsal  motor  93  94  Pontobulbar  L o c o m o t o r S t r i p (PLS)  Electrical (PLS)  elicited  ranging  from  stimulation locomotor  of the pontobulbar  locomotor  movements a t low t h r e s h o l d  30-80jiA i n n i n e a n i m a l s .  In four  intensities  out o f four  following the establishment of a locomotion producing stimulation (25-100mM) behaviour  site  (walking)  i n t o PLS e l i c i t e d  In the  The s t e p p i n g  (mean 23 m i n u t e s :  electrical  stimulation  initial  range  injection (Figure  of carbachol walking  to the f i r s t o f 8.2  minutes  11B) was l o n g  7-45 m i n u t e s ) ,  enhanced t h e v i g o r  birds,  electrical  a pattern of alternating  following  (range 2.2-12 m i n u t e s ) .  intensity  11A), i n j e c t i o n  (no w i n g f l a p p i n g ) w i t h a mean l a t e n c y  d e t e c t a b l e movement  lasting  (Figure  strip  d u r i n g which  of walking  time  i n an  d e p e n d e n t manner.  t h e only animal  same s i t e  tested,  infusion  of atropine  during carbachol-induced locomotion  (25mM)  into  completely  blocked not only the chemically induced behaviour but also a l l electrically intensity  evoked  intermittent  of pilocarpine  short  animal w i t h a time maintained  (50mM) i n t o  bursts of walking t o onset  8 minutes.  e x t e n s i o n o f b o t h wings and l e g s , was i n e f f e c t i v e  Neither was e f f e c t i v e  scopolamine  behaviour  i n one  The b u r s t s were  T h i s p e r i o d was f o l l o w e d  a t which time  electrical  at e l i c i t i n g locomotor p a t t e r n s .  (N=l) (25mM) n o r n i c o t i n e  at blocking,  PLS e l e c t r i c a l l y  PLS p r o d u c e d  and f l y i n g  o f 7 minutes.  f o rapproximately  stimulation  of  stimulation  (170MA).  Introduction  by  s t e p p i n g up t o t h e maximal  e l i c i t i n g or changing  stimulated locomotion.  95  (N=2) (25mM)  the threshold  Figure  11.  activity  Electromyographic  elicited  injection  by e l e c t r i c a l  into the pontobulbar  Alternating  records  (LITC)  locomotor  iliotibialis  strip  ( P L S ) . A:  s t e p p i n g EMGs e l i c i t e d  i n t o t h e same  site.  96  from t h e r i g h t  c r a n i a l i s muscles  f l e x o r m u s c l e ) e l i c i t e d by e l e c t r i c a l  (lOOmM)  locomotor  s t i m u l a t i o n and c a r b a c h o l  s t e p p i n g r e p r e s e n t e d by EMG p a t t e r n s  (RITC) a n d l e f t  Alternating  (EMGs) s h o w i n g  (major h i p  s t i m u l a t i o n o f t h e PLS. B:  by i n j e c t i o n  of carbachol  A  1s e c  97  C e n t r a l Nucleus,  Infusion medullary in  d o r s a l p a r t (Cnd)  o f carbachol  c e n t r a l nucleus  o n l y one o f f i v e  birds  (lOOmM) i n t o t h e d o r s a l p a r t o f t h e (Cnd) p r o d u c e d tested  long l a s t i n g  ( F i g . 12A,B). I n two a n i m a l s ,  however, t h e t h r e s h o l d s f o r e l e c t r i c a l l y reduced  (60/nA t o 30/iA a n d 80LLA t o 60/iA)  50mM) i n f u s i o n . stimulated further  chemically one.of  after  Introduction of atropine  t o induce  locomotion  (carbachol). Similarly,  t h e animals  that  Scopolamine  carbachol  were  (llmM &  (30mM) d u r i n g c a r b a c h o l locomotion,  a s w e l l as  e l e c t r i c a l l y and  introduction  showed d e c r e a s e d  30mM) c o m p l e t e l y b l o c k e d any f u r t h e r activity.  evoked locomotion  locomotion b l o c k e d t h e ongoing  attempts  stepping  of atropine into  threshold (carbachol,  electrically  evoked  (25mM) d i d n o t change t h e  carbachol-induced decrease  i n locomotor  threshold o f the other  animal.  C e n t r a l Nucleus,  In  thev e n t r a l part o f themedullary  electrical position, out  stimulation,  Subsequent behaviour  used  elicited bilateral  o f 10 b i r d s ,  to establish  nucleus  t o carbachol injection, i n another.  long l a s t i n g  walking  ( F i g . 13, c a r b a c h o l =  and f l y i n g  behaviour i n  while e l e c t r i c a l Two a n i m a l s  98  in 9  i n 1 o u t o f 10.  injected  showed b o t h w a l k i n g  (Cnv),  optimum e l e c t r o d e  o f carbachol produced  i n 6 o f t h e 10 a n i m a l s  w a l k i n g was r e d u c e d  central  a l t e r n a t i n g hindlimb walking  and r u n n i n g and f l y i n g  injection  27mM). One b i r d response  v e n t r a l p a r t (Cnv)  threshold for  demonstrated  no  Figure  12.  activity  Electromyographic  elicited  injection  stepping  (RITC) and l e f t electrical  EMGs e l i c i t e d same  by e l e c t r i c a l  (EMGs) s h o w i n g  stimulation  and  into the c e n t r a l medullary nucleus,  A: A l t e r n a t i n g  by  records  (LITC)  carbachol  dorsal  r e p r e s e n t e d by EMG p a t t e r n s iliotibialis  stimulation  cranialis  locomotor  part  from r i g h t  muscles  o f t h e Cnd. B: A l t e r n a t i n g  by i n j e c t i o n o f c a r b a c h o l  site.  99  (Cnd).  (lOOmM/1.Oul)  elicited stepping into the  A  2 sec  100  Figure  13.  Electromyographic  records  activity  elicited  by e l e c t r i c a l  infusion  into the c e n t r a l medullary  PRESTIM: EMGs f r o m r i g h t c r a n i a l i s muscles activity  stepping  shown by t h e s q u a r e s  (LITC)  (filled  stimulation  locomotor  p r e p a r a t i o n . STIM: f r o m t h e same  (40LLA) o f t h e s i t e  (Cnv)  s e c t i o n through the caudal  CARB: C a r b a c h o l  square) e l i c i t e d  (Cnv).  iliotibialis  by EMG p a t t e r n s  i n the coronal  (bottom r i g h t ) .  ventral part  t h e l a c k o f spontaneous  represented  muscles d u r i n g e l e c t r i c a l  site  nucleus,  (RITC) and l e f t  illustrating  locomotor  s t i m u l a t i o n and c a r b a c h o l  i n the pre-stimulation decerebrate  Alternating  medulla  (EMGs) s h o w i n g  injection  alternating  i n t o t h e same  stepping,  as  d e m o n s t r a t e d b y t h e EMGs f r o m RITC a n d L I T C . ATRO: The carbachol-induced atropine after of  (unfilled  atropine  the s i t e ,  EMG  square)  injection,  stimulus  locomotor p a t t e r n s the  locomotor a c t i v i t y  was b l o c k e d  i n t o t h e same s i t e .  by i n j e c t i o n o f  In a d d i t i o n ,  as shown d u r i n g e l e c t r i c a l  intensities  (some s t i m u l u s  traces).  101  stimulation  up t o 170LLA d i d n o t evoke b l e e d t h r o u g h c a n be s e e n i n  PRESTIM  RITC  LITC H i sec-*  STIM  Msec 4  C A R B m».  imi  11  » — >! - f r . ,„fcRITC  <•» • » - 4 4* f « + H "  | • I • LITC »-5sec-«  effects  of carbachol i n j e c t i o n .  atropine  (25mM)  following  Five  carbachol-induced  including the walking/flying bird, within all  a mean t i m e  animals  ceased  injected  with  locomotion,  a l l locomotor  o f 7.5 m i n u t e s p o s t - i n j e c t i o n  activity  ( F i g . 13). In  c a s e s where c a r b a c h o l - i n d u c e d l o c o m o t i o n was b l o c k e d by  atropine,  locomotion  stimulation  d u r i n g t h e e x p e r i m e n t a l p e r i o d . However, t h e r e t u r n  of e l e c t r i c a l l y injection higher  d i d n o t r e t u r n i n t h e absence o f e l e c t r i c a l  stimulated locomotion  appeared  to relate  to the concentration injected,  concentrations of atropine  f o r p e r i o d s o f up t o 40 m i n u t e s Injections  of nicotine  following atropine  (50mM  (range  25-50mM) b l o c k i n g  ( s t i m u l a t i o n maximum  (N=2)  with  170^A).  (lOOmM) a n d p i l o c a r p i n e  (N=2)  (50mM) were i n e f f e c t i v e  at producing  l o c o m o t i o n when i n f u s e d  i n t o Cnv a n d d i d n o t a p p e a r t o have any  effect  on e i t h e r  electrical effect  Pontine  the t h r e s h o l d or type  stimulation.  when i n j e c t e d  Scopolamine  into this  (RP) a n d M e s e n c e p h a l i c  Injection formation locomotor  of carbachol  (RPgc)  (MRF) R e t i c u l a r  (54mM)  (lOOmM) i n j e c t i o n  second  at e l i c i t i n g  stimulation  on e l e c t r i c a l l y  103  reticular stimulated  p a t t e r n . I n t h e MRF, decreased  the e l e c t r i c a l  (100—>60fiA)  locomotion  threshold intensity  bird.  Formation  into the pontine  s t i m u l a t i o n t h r e s h o l d f o r locomotion  electrical  e l i c i t e d by  site.  t h r e s h o l d o r on l o c o m o t o r  was i n e f f e c t i v e  o f locomotion  (N=l) (25mM) a l s o h a d no  (N=l) h a d no e f f e c t  however, c a r b a c h o l  but  chemically stimulated  i n one a n i m a l ,  or changing the f o r locomotion  ina  M e d i a l L o n g i t u d i n a l F a s c i c u l u s (MLF)  Electrical and  stimulation  forelimb locomotion  evoked w a l k i n g  alone  (70-80uA) o f t h e MLF e v o k e d  i n five birds.  walking  Injection  i n three out o f f i v e  of carbachol  animals  were i n i t i a l l y  the stimulation  (27-100mM)  evoked  (N=l) ( F i g . 14B) o r r u n n i n g a n d f l y i n g  animals and  sites  intensities  ( F i g . 14A) w h i c h gave way t o f l y i n g and  running at higher i n t e n s i t i e s . into these  Low s t i m u l u s  hindlimb  either  (N=2). The  e l e c t r i c a l l y stimulated, then  intensity  necessary  t o evoke  curarized,  locomotor  p a t t e r n s was i n c r e a s e d o v e r t h e p r e - p a r a l y z e d c o n d i t i o n t o a mean i n t e n s i t y  o f 170uA  concentrations  of carbachol necessary  patterns not  (see Chapter  i n these paralyzed birds  significantly  different  6 ) . However, t h e t o evoke  (^fictive'  from t h o s e  found  locomotor  locomotion)  were  i n unparalyzed  preparations.  COMPARISON  The  BETWEEN ELECTRICAL AND CHEMICAL STIMULATED LOCOMOTION  locomotion  e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n  varied with d i f f e r e n t  intensities  to  (Sholomenko and S t e e v e s ,  region i n the bird  example, at  low c u r r e n t i n t e n s i t y  higher  intensity  intensity other and  e l e c t r i c a l stimulation  a n d from  region  1987). F o r  i n some s i t e s p r o d u c e d  walking  ( e . g . 30uA), r u n n i n g a n d f l y i n g a t  ( e . g . 90fxA) and f l y i n g a l o n e  ( e . g . 120uA)  sites,  of stimulation  typically  (see F i g . 3 , S t e e v e s  threshold intensity  f l y i n g together, while  e t al.,  higher  1987). In  s t i m u l a t i o n would, evoke  in still 104  at s t i l l  other locations,  only  running  Figure  14.  activity injection  elicited  left  stimulation carbachol  stepping  (LITC)  records  by e l e c t r i c a l  i n t o the medial  Alternating and  Electromyographic  (EMGs) s h o w i n g  stimulation  longitudinal  as r e p r e s e n t e d  iliotibialis  cranialis  i n t o t h e same  105  and c a r b a c h o l  fasciculus  (MLF). A:  by EMGs f r o m r i g h t  o f t h e MLF. B: A l t e r n a t i n g (27mM) i n f u s i o n  locomotor  muscles d u r i n g  (RITC) electrical  s t e p p i n g EMGs e l i c i t e d by site.  LITC  M- "•*» "4 ^ 111,1  >>IIM  m  *"* I 1  106  sec  w a l k i n g c o u l d be e l i c i t e d However, e l e c t r i c a l  at a l l stimulation  stimulation  intensities.  a l w a y s e v o k e d t h e same  of behaviour i n a s t i m u l a t i o n  dependent  manner. Thus,  i n t h e same s i t e  the  repeated t r i a l s  same l o c o m o t o r p a t t e r n .  were r e p l i c a t e d by t h e  and s i t e  These p a t t e r n s ,  neurochemical  locomotion.  107  specific  always  with  pattern  few  i n j e c t i o n s which  elicited exceptions, elicited  DISCUSSION  mid-  Neurochemical  stimulation of selected regions  and h i n d b r a i n  elicited  decerebrate agonists  locomotion will as  a spectrum o f locomotor p a t t e r n s i n  b i r d s . My r e s u l t s  evoke l o c o m o t i o n  demonstrated that c h o l i n e r g i c  and m u s c a r i n i c  antagonists  when i n j e c t e d i n t o a v a r i e t y o f s i t e s .  be d i s c u s s e d  r e g i o n by r e g i o n  from b i r d s w i l l  mammalian s p e c i e s  f o r which s i m i l a r  P o n t o b u l b a r Locomotor  Electrical (PLS) al.,  elicits  results  will  be drawn  data  involved.  those  found i n  exists.  Strip  stimulation of the pontobulbar  locomotion  submitted)  be compared w i t h  block  These  and c o n c l u s i o n s  t o t h e p o s s i b l e a v i a n n e u r o a n a t o m i c a l pathways  These d a t a  i n the avian  i n birds  (Steeves  locomotor  strip  e t al., 1987; Funk e t  and i n a w i d e r a n g e o f v e r t e b r a t e  species  from  0  lamprey t o c a t ( f o r review, As  will  be d i s c u s s e d  neuroanatomical similar  t o those  exception  i n greater  input/output  r e l a t i o n s of the avian  t h a t t h e major t r i g e m i n o t h a l a m o c o r t i c a l  projection  1986).  d e t a i l below, t h e  found i n a v a r i e t y o f v e r t e b r a t e s  mammals i s r e p l a c e d  Wild  see Chapter 1 & M c C l e l l a n ,  TTD a r e with the  r e l a y found i n  i n b i r d s by a d i r e c t t e l e n c e p h a i i c  (Arends e t al., 1984; A r e n d s a n d Dubbeldam, 1984;  e t al., 1 9 8 4 ) . My p r e v i o u s  stimulation of Horsley  studies  i n b i r d s demonstrate t h a t  of the descending t r i g e m i n a l nucleus (PH) , i n a d d i t i o n t o a d j a c e n t 108  regions  electrical  and t h e Plexus of the  pontomedullary  l a t e r a l r e t i c u l a r formation ( p a r v o c e l l u l a r  r e t i c u l a r n u c l e u s ) , which are v i r t u a l l y i n d i s t i n g u i s h a b l e from t h e n u c l e u s i n t e r p o l a r i s o f TTD e l i c i t s locomotion  (Arends and Dubbeldam, 1984),  i n the decerebrate  a n i m a l , thus d e f i n i n g t h i s  a  r e g i o n as the a v i a n e q u i v a l e n t o f t h e mammalian PLS al.,  (Steeves  et  1987). In my experiments,  l o c o m o t i o n was  e l i c i t e d by i n t r o d u c t i o n  o f c a r b a c h o l or p i l o c a r p i n e i n t o the PLS. C a r b a c h o l ,  a  c h o l i n e r g i c agonist with a s t r u c t u r e s i m i l a r to that of acetylcholine  ( T a y l o r , 1985)  i s an e f f e c t i v e c h o l i n o m i m e t i c  at  b o t h n i c o t i n i c and m u s c a r i n i c a c e t y l c h o l i n e r g i c r e c e p t o r subtypes (Burgen,  1983), i n c l u d i n g f o u r c u r r e n t l y r e c o g n i z e d  m u s c a r i n i c r e c e p t o r subtypes which have been i d e n t i f i e d i n the CNS  (Buckley e t a l . ,  1988). R e c e p t o r b i n d i n g s t u d i e s demonstrate  t h a t c a r b a c h o l b i n d s t o h i g h and low a f f i n i t y r e c e p t o r s i n the CNS,  a l t h o u g h t h e b i n d i n g v a r i e s by a f a c t o r o f 100  upon the l o c a t i o n  (Burgen,  depending  1983). The b i n d i n g s t u d i e s a l s o  demonstrate t h a t at c a r b a c h o l c o n c e n t r a t i o n s o f lOOmM, a l l muscarinic al.,  (Mi & M2) r e c e p t o r s i t e s s h o u l d be bound ( P o t t e r et  1983). Thus, a t the s i t e o f c a r b a c h o l i n j e c t i o n  locomotor  into  r e g i o n s i n t h e a v i a n b r a i n at h i g h c o n c e n t r a t i o n s  (lOOmM), a l l m u s c a r i n i c r e c e p t o r s s h o u l d be a c t i v a t e d . I t was not p o s s i b l e t o determine,  however, t h e c o n c e n t r a t i o n g r a d i e n t  from the i n j e c t i o n p o i n t t o the p e r i p h e r y o f the a f f e c t e d volume. In t h i s study, i t was  a l s o not p o s s i b l e t o d i s t i n g u i s h  between t h e d i f f e r e n t r e c e p t o r subtypes a c t i v a t e d , as  no  a g o n i s t s or a n t a g o n i s t s are y e t a v a i l a b l e which are s p e c i f i c f o r a s i n g l e m u s c a r i n i c r e c e p t o r subtype (Buckley e t al.,  1988).  Therefore, induced  i t was d i f f i c u l t  t o d i s t i n g u i s h between t h e c a r b a c h o l  a c t i v a t i o n of muscarinic  receptors  p o t a s s i u m c o n d u c t a n c e i n some n e u r o n s , c o n d u c t a n c e i n some n e u r o n s , importantly calcium  2) d e c r e a s e t h e p o t a s s i u m  come i n d e t e r m i n i n g  a c t i v a t e d by i n j e c t i o n  (North,  although  of the muscarinic  with  differing  a l l muscarinic  lends  receptors  are involved i n the a c t i v a t i o n ,  Further responsible  credence t o the hypothesis  evidence  Atropine  c o u l d be b l o c k e d atropine  a l l muscarinic  w h i c h h a s no n i c o t i n i c  can  receptors  underlying  h a d no e f f e c t  However, s c o p o l a m i n e ,  atropine,  of a role  forthis  a potent  carbachol  site.  antagonist 1983), and  this  result  f o r muscarinic  suggestion  from  this  comes f r o m t h e  cholinergic nicotinic  when i n j e c t e d i n t o t h i s muscarinic  110  as b e i n g  1983). However, a s  the a c t i v a t i o n of locomotion  finding that nicotine, the c l a s s i c agonist,  agonist  of the  (Mitchelson,  (Mitchelson,  suggestive  r e g i o n . C o r r e l a t i v e support  receptor  was t h a t  s u l f a t e i n t o t h e same  a s i n g l e PLS s i t e was i n j e c t e d w i t h o n l y be c o n s i d e r e d  this  receptors  by i n j e c t i o n  receptors  action  1983).  only.  h a s b e e n d e m o n s t r a t e d as a n o n - s e l e c t i v e  which b l o c k s  only  although  implicating muscarinic  antagonist  (Brown,  receptor  that cholinergic  f o r the i n d u c t i o n of locomotion  locomotion  subtype  following pilocarpine  injection  i n a single t r i a l  receptor  agonist p i l o c a r p i n e  affinities  However, t h e a c t i v a t i o n o f l o c o m o t i o n  was e m p l o y e d  1985). S i m i l a r  the s p e c i f i c  i n t o t h e PLS, a s p i l o c a r p i n e r e c o g n i z e s  muscarinic  (most  sodium) c o n d u c t a n c e i n some n e u r o n s o r 4) r e d u c e  difficulties  induced  increase  3) i n c r e a s e t h e c a t i o n  c o n d u c t a n c e i n some n e u r o n s  subtypes,  w h i c h 1)  antagonist  region.  (Kilbinger,  1983),  rather unexpectedly  stimulation-induced animal.  a l s o had  locomotion  T h e s e above r e s u l t s  equivocal, receptors  do  suggest  underlying  supported,  the  i n p a r t , by  studies discussed  bird,  region  e t a l . , 1988  contains  the  observed r e s u l t s . i n p u t s t o TTD to  localize the  has  (SG)  see  dextran  type  SG  Steeves,  of receptor our  utilized  arise  (Steeves  This  study  (Glover  unpublished  and  has  binding  reticular  nucleus  oral part  (RL),  e t a l . , 1986)  our  attempt  regions,  techniques  our  to  retrograde  rhodamine  i n t o TTD to  conjugated  (Webster  and  locate putative  region.  These f i n d i n g s  of c h o l i n e r g i c input  i n c l u d i n g the  reticular  bodies  unpublished  gigantocellular reticular  of the pontine  this  (ChAT) c o n t a i n i n g c e l l  f l u o r e s c e i n - and  formation,  in  spinal  i n b i r d s . In an  Taccogna,  observations)  studies  knowledge, no c h o l i n e r g i c  f r o m ChAT p o s i t i v e n e u r o n s o r i g i n a t i n g i n : 1)  reticular  also  which c o r r e l a t e s with  b e e n combined w i t h  that p o s s i b l e sources  medullary  one  localization  m e d u l l a and  immunohistochemical  cholinergic projections into this indicate  are  1 H , J , K , G , I ) . Thus,  have b e e n r e p o r t e d  studies using  amines  in  of c h o l i n e r g i c receptors  of the  Figure  However, t o  avian b r a i n  transport  and  receptor  (AChM a n t a g o n i s t )  choline acetyltransferase  observations).  and  results  i s o l a t e p o s s i b l e c h o l i n e r g i c inputs to these  laboratory  in  or  PLS  below.  substantia gelatinosa  (Dietl  electrical  somewhat  The  n e u r o a n a t o m i c a l and  i n p i g e o n b r a i n show h e a v y l a b e l l i n g  cord,  while  observed r e s u l t s .  3  and  on  for c h o l i n e r g i c muscarinic  N-[ H]methylscopolamine  TTD  effect  when i n j e c t e d i n t o t h e  i n the  a role  no  formation  t o TTD the  may  pontine  lateral nucleus  (Rgc)  (RPO), 2)  the  nuclei  o f V I I , which send  t h e obex, 3)  the descending  projects to rostral pallidus, nucleus,  v e s t i b u l a r nucleus  r e g i o n s o f TTD, 4)  which impinges  localized  locomotion  from  mammals,  glossopharyngeal  (CCK),  this  and subserve  a f f e r e n t s from nerves  been  1983)  PPN/mMLR may s e n d  1985)  1984)  formation  fibres  t o TTD  and R e i n e r ,  1987). Other caudal  1987)  i n n e r v a t i o n t o PLS  i n t u r n , p r o j e c t upon t h e pathways  MesV i s known t o s e n d  (Garcia-Rill  e t al.,  has b e e n f o u n d  1983;  Ikeda e t  i n t h e MesV  1987). T h i s p r e c l u d e s t h e p o s s i b i l i t y i n p u t t o TTD  possible cholinergic  cuneiform  ( V i n c e n t and R e i n e r ,  and p r o p r i o s p i n a l  b u t no ChAT a c t i v i t y  MesV p r o v i d e s c h o l i n e r g i c  localized  which,  a b o v e . A l s o i n mammals,  internuclear  (Vincent  cells  a small cholinergic  (Garcia-Rill,  (VIP) a n d s o m a t o s t a t i n  but are apparently not c h o l i n e r g i c .  of  outlined  the carbachol-induced  t h e t r i g e m i n a l and  polypeptide  the cat the ChAT-containing  reticular  may  t o c o n t a i n S u b s t a n c e P, c h o l e c y s t o k i n i n  vasoactive intestinal  brainstem  interneurons  i m p i n g e on t h e d e s c e n d i n g t r i g e m i n a l  In  the  n u c l e u s and  region.  (Dubner and B e n n e t t ,  al.,  subceruleus  that i n t r i n s i c cholinergic  and a r e thought  neurons  the parabrachial  TTD. ChAT c o n t a i n i n g n e u r o n s have a l s o  m o d u l a t e TTD n e u r a l c i r c u i t s  nucleus  raphe  t o TTD a n d t h e s u b t r i g e m i n a l n u c l e a r r e g i o n s , a l l o w i n g  the p o s s i b i l i t y  In  which  t h e paramedian  TTD and 6)  ventral to the ventral  projects to rostral  (VeD),  the nucleus  TTD, 5)  on r o s t r a l  also projecting to rostral  r e g i o n which l i e s  for  e f f e r e n t s t o TTD i n r e g i o n s c a u d a l t o  nucleus,  that  ( R e i n e r and V i n c e n t ,  i n p u t s t o TTD may a r i s e  from  where b o t h ACh and AChE have b e e n  i n the r a t (Palkovits  and J a c o b o w i t z ,  112  1974;  Ramon-Moliner and Dansereau, 1 9 8 1 ) . However,  1974) and c a t (Kimura et al.,  some c o n t r o v e r s y  cuneiform nucleus contains  e x i s t s as t o whether t h e  ACh n e u r o n s ,  as R e i n e r and  (1987) f o u n d no e v i d e n c e o f ChAT c o n t a i n i n g nucleus  Vincent  neurons i n t h i s  ( f o r r e v i e w s e e p . 521 o f Rye e t al.,  1981).  P h a r m a c o l o g i c a l e v i d e n c e o f a r o l e f o r ACh i n TTD stimulation-induced  l o c o m o t i o n has a l s o been found i n t h e r a t  where i o n t o p h o r e t i c  a p p l i c a t i o n o f ACh i n c r e a s e d  cells  i n the nucleus caudalis  While,  o f TTD  (Salt  firing  and H i l l ,  t o o u r knowledge, no c h o l i n e r g i c a f f e r e n t s  we i n j e c t e d have b e e n u n e q u i v o c a l l y studies  point  may p l a y  established  rates of  1981).  t o the region  i n b i r d s , our  t o s e v e r a l p o t e n t i a l c h o l i n e r g i c pathways which  some r o l e i n l o c o m o t o r c o n t r o l v i a t h e PLS pathway.  However, t h e p r e c i s e  r o l e of these projections  i n motor  control  r e m a i n s t o be d e t e r m i n e d . In b i r d s , including ST,  TTD e f f e r e n t s p r o j e c t  cerebellum,  s p i n a l cord  PH, RL, Rpc, d o r s a l  nucleus  dorsal  (Arends a n d Dubbeldam,  p r o j e c t i o n may be e q u i v a l e n t n e t w o r k f o u n d i n mammals,  communication).  while the efferents  n u c l e i have b e e n i m p l i c a t e d  grasping,  feeding  below i n r e l a t i o n  parabrachial  The s p i n a l  cord  propriospinal t o P r V and t h e  i n the control of  i n birds  C o n n e c t i o n s o f TTD w i t h t h e r e t i c u l a r  On t h e b a s i s  ( C 4 ) , Cnv, Cnd,  t o the trigeminal  and p e c k i n g  regions  1982, 1984; A r e n d s e t al., 1984;  reticular  regions.  horn  column n u c l e i , P r V , and  Webster and Steeves, p e r s o n a l  discussed  to a variety of  (Wild  e t al.,  1984).  formation n u c l e i w i l l  t o locomotion e l i c i t e d  of i t s hodological  with i t s locomotor e l i c i t i n g p r o p e r t i e s  from  connections, following  be  these  combined  electrical  and  chemical in  stimulation,  the sensory  birds. and  This  the  data, therefore,  that  (Jordan,  a major  role  agrees  w i t h t h e p r o p o s a l by  Jordan  1986; Noga e t a l . , 1988) f o r mammalian  the descending  sensorimotor  this  to play  c o n t r o l o f a v a r i e t y o f motor b e h a v i o u r s i n  co-workers  species  however, TTD a p p e a r s  trigeminal  nucleus  i s concerned  c o n t r o l o f l o c o m o t i o n . Our s t u d i e s  c o n t r o l i s mediated,  i n part,  with  suggest  that  by c h o l i n e r g i c m u s c a r i n i c  mechanisms.  Central  Nucleus,  Previous  dorsal part  studies  the d o r s a l part  (Cnd)  have shown t h a t  of the medullary  electrical  stimulation of  c e n t r a l nucleus  (Cnd) e l i c i t s  locomotion  i n the decerebrate b i r d  ( S t e e v e s e t al.,  Retrograde  transport  True  1987)  a n d HRP  rise,  i n part,  spinal  (Cabot  studies  using  e t al.,  1982) d e m o n s t r a t e d  cord v e n t r a l  voluntary  or e l e c t r i c a l l y  decerebrate birds  1 9 8 1 ) . Thus, give  rise  control  induced walking both  1980; E i d e l b e r g , i t appears  that  t o a descending  Cnd  gives  i n the  through  i n chronic  1987b),  1981) and monkey cells  al.,  c a t (Steeves  (Eidelberg et  o r i g i n a t i n g from  pathway i m p o r t a n t  and  this  al,,  nucleus  f o r the descending  of locomotion.  comes f r o m  receives  et  l e s i o n s , t o be e s s e n t i a l f o r  (Sholomenko a n d S t e e v e s ,  Further evidence birds  that  f u n i c u l u s , w h i c h have b e e n shown  low t h o r a c i c s p i n a l c o r d  Jordan,  (Steeves  to the r e t i c u l o s p i n a l f i b e r s t r a v e l l i n g  selective  and  Blue  1986).  f o r a r o l e o f Cnd i n l o c o m o t o r  neuroanatomical  afferent input  studies  control i n  w h i c h show t h a t  from t h e s u b n u c l e i  c a u d a l i s and  Cnd  interpolaris 1984),  o f TTD  the nucleus  communication), archistriatum (Wild,  1985,  e t al.,  (Arends  1984;  intercollicularis  the tectum intermedium  (Hunt  A r e n d s and  (ICo)  (Webster,  and K u n z l e ,  1976)  W i l d e t a l . , 1984).  The  afferent  terminating  reticular  the pigeon tectal appears basal  i n the pontomedullary  (Hunt  t o be p a r t  ganglia  et  a l . , 1984).  motor n u c l e i reticular  of c r a n i a l  1984),  component. The nuclei,  and FRL  al., The  (Rgc)  Cnd,  1982;  efferent  sends  nerves V and  p l a c e Cnd  which i s  motor c o n t r o l  (Reiner  ascending p r o j e c t i o n s to & VII,  the  gigantocellular  t o have d i r e c t  1975)  our r e s u l t s  and w i l l  c o n n e c t i o n s o f Cnd  1982).  1982)  (Arends  and  reticulospinal reticular  sensorimotor  above. In b i r d s ,  ICo,  t o c o n t a i n n e u r o n a l p o p u l a t i o n s homologous  o f f e e d i n g and  Dubbeldam,  nucleus/tectum,  f r o m PLS/TTD t o b r a i n s t e m  appear  deep  i n v o l v i n g the avian  the p a r a b r a c h i a l nucleus  n e r v e V and V I I motor n u c l e i control  circuit  i n t h e t h e mammalian c u n e i f o r m n u c l e u s  Edwards,  the  R e i n e r and K a r t e n ,  in visuo-spatial  as d i s c u s s e d f r o m  found  of a  from t h e  i n a d d i t i o n to i t s descending  are thought  to those  1976;  spiriform  Cnd  projections  including  implications  involved  the  f o r m a t i o n which i s  I n p u t t o Cnd  of the outflow c i r c u i t  In t u r n ,  nucleus  Dubbeldam,  and K u n z l e ,  (TPc)/lateral  p o s t u l a t e d t o be  from  o f f e e d i n g , g r a s p i n g and p e c k i n g i n  ( W i l d e t a l . , 1984).  layers  and  i n p u t from  as b e i n g p a r t  f o r the c o n t r o l  personal  v i a the o c c i p i t o m e s e n c e p h a l i c t r a c t  a r c h i s t r i a t u m has b e e n i m p l i c a t e d  essential  Dubbeldam,  be  this  drinking behaviours  These h o d o l o g i c a l  i n an e x c e l l e n t  position  et  discussed subsequently.  to the p a r a b r a c h i a l  implicate  (Cabot  and  cranial  region i n the (Arends  relationships, t o a c t as an  and therefore,  integratory  and  d e s c e n d i n g output r e g i o n from which b o t h sensory  and h i g h e r  b r a i n c e n t e r s may i n f l u e n c e motor c o n t r o l . To f u r t h e r our u n d e r s t a n d i n g  o f Cnd's r o l e i n locomotor  c o n t r o l , we have begun t o examine i t s neuropharmacology. Carbachol  i n f u s i o n i n t o Cnd e l i c i t e d  walking behaviour  (or reduced t h r e s h o l d f o r )  which was b l o c k e d by t h e m u s c a r i n i c  antagonist  a t r o p i n e , w h i l e n i c o t i n i c a g o n i s t s were i n e f f e c t i v e a t p r o d u c i n g locomotion  o r changing t h e t h r e s h o l d f o r e l e c t r i c a l l y  stimulated  locomotion. Autoradiographic  studies of receptor binding with  N - [ H ] m e t h y l s c o p o l a m i n e i n d i c a t e t h e presence o f m u s c a r i n i c 3  c h o l i n e r g i c r e c e p t o r s i n t h e Cnd o f t h e p i g e o n 1988). A l t h o u g h  ( D i e t l et a l . ,  no c h o l i n e r g i c a f f e r e n t s t o Cnd have been  u n e q u i v o c a l l y i d e n t i f i e d i n b i r d s , neuroanatomical Steeves,  unpublished'observations)  and immunohistochemical  s t u d i e s from our l a b o r a t o r y (Steeves observations) bodies  (Webster and  and Taccogna,  unpublished  demonstrate t h e p r e s e n c e o f ChAT c o n t a i n i n g c e l l  i n the subtrigeminal nucleus,  TTD, p o n t i n e  formation, l a t e r o d o r s a l tegmental nucleus  reticular  and n u c l e u s i s t h m i ,  p a r s p a r v o c e l l u l a r i s , a l l o f which have been shown t o p r o j e c t t o Cnd.  Cnd i t s e l f a l s o c o n t a i n s ChAT p o s i t i v e neurons. S i m i l a r l y , i n mammals, t h e e q u i v a l e n t s t r u c t u r e , FTL,  ( l a t e r a l t e g m e n t a l f i e l d ) r e c e i v e s a f f e r e n t i n p u t from t h e r e g i o n o f t h e P L S / t r i g e m i n a l area  (Noga e t a l . , 1988;  G a r c i a - R i l l e t al.,1983b) and a l s o appears t o r e c e i v e d e s c e n d i n g c h o l i n e r g i c i n p u t from t h e MesV r e g i o n and PPN/mMLR ( G a r c i a - R i l l et a l . , 1983b). F u r t h e r , i n c a t , c e l l b o d i e s  c o n t a i n i n g ChAT  have been l o c a l i z e d i n t h e r e t i c u l a r t e g m e n t a l f i e l d  (Vincent  and R e i n e r , neurons  1987),  possibly  implicating  results.  Taken t o g e t h e r w i t h t h o s e  from mammalian s t u d i e s , o u r  r e s u l t s provide strong evidence that  for  o f the descending locomotor  control  as an i n t e g r a t i o n  structures  controlling  locomotor  locomotion  from h i g h e r  i n birds. elicited  t h e nucleus appears  cholinergic muscarinic control  Based  locomotion  possible that  control  scopolamine  injected  awaits  cholinergic over t h i s  input  C e n t r a l Nucleus,  The locomotor  may a l l e v i a t e  replication.  i t may be  this  volumes'  problem.  Also,  i n t h e one a n i m a l  Future studies  are also  b o t h t h e mechanisms a n d s o u r c e ( s ) o f  (or i n t r i n s i c  descending  directly  smaller injection  d i d not block locomotion  r e q u i r e d t o determine  animal  s p r e a d t o Cnv o r TTD was r e s p o n s i b l e  spread)  further  under  pathways  following carbachol infusion,  neurochemical  with less  on t h e  t o be i n p a r t  and p o s s i b l e  for the locomotion. Studies u t i l i z i n g (presumably  brain  atropine-reversible  have b e e n d e s c r i b e d . However, a s o n l y a s i n g l e demonstrated  to act  i n f o r m a t i o n from t h e  n u c l e u s and a l s o  carbachol injection  behaviour,  give rise to  r e t i c u l o s p i n a l pathway w h i c h i s e s s e n t i a l  centre f o r sensory  trigeminal  findings that  Cnd n e u r o n s  i n v e r t e b r a t e s . F u r t h e r , i t appears  descending  why  cholinergic  a n d m u s c a r i n i c r e c e p t o r s as p r o d u c i n g some o f t h e  observed  part  intrinsic  n e u r o n s ) w h i c h may e x e r t  control  pathway.  v e n t r a l p a r t (Cnv)  Cnv a l s o control.  appears  t o p l a y and important  Electrical  stimulation  role i n  of the ventral part of  the medullary  central  ( S t e e v e s e t al., from  the b i r d  nucleus  1986;  (Cnv)  Sholomenko and  (Sholomenko and  ( S t e e v e s and  Jordan,  demonstrated  that  produced  1980)  a lesion  i n the  spinal  cord ventral  i n the  intact  animal  and  locomotion  Steeves,  Steeves,  and monkey  1987),  1987b). as  Evidence  i n the cat e t al.,  (Eidelberg  of the descending  in birds  1984),  pathways  travelling  funiculus blocks voluntary  locomotion  electrically  s t i m u l a t e d locomotion  in  the decerebrate p r e p a r a t i o n . In t h e  cat, G a r c i a - R i l l ' s  1987b) u t i l i z e d yellow  from  t h e VRN  central  electrically/chemically  and  gray,  and  reticular  nucleus,  lateral  formation c e l l s .  subcuneiform  formation, a n t e r i o r  reticular Steeves  and  and  Jordan  from  the  reticular (1970a)  PPN,  reticular  (1984) u t i l i z e d  while Orlovsky,  in  reticular  scattered  and m e d u l l a r y  sites  nucleus,  lateral  nuclear  found  anterograde  amino a c i d s t o d e m o n s t r a t e  p r o j e c t i o n s to the pontine MLR,  nucleus  and  of radioactive  from t h e c l a s s i c a l  i n p u t . They  p r o j e c t i o n s t o VRN  cuneiform nucleus,  Skinner,  d e f i n e d locomotor  i t s afferent  contralateral  midbrain  transport  (Garcia-Rill  retrograde t r a n s p o r t of bisbenzimide  t o demonstrate  ipsilateral  group  direct formation  used  e l e c t r o p h y s i o l o g i c a l t e c h n i q u e s t o show a m o n o s y n a p t i c l i n k a g e between t h e  1MLR  In b i r d s , demonstrate  and  medullary  neuroanatomical  that  cells  i n Cnv  reticular  retrograde transport studies give r i s e  neurons t r a v e l l i n g  the  funiculus  e t a l . , 1987;  that  (Steeves  electrical  locomotion  length of the  stimulation  (Steeves  e t al.,  formation.  to  reticulospinal  spinal  W e b s t e r and  i n and  around  Steeves,  these c e l l s  1 9 8 7 ) . In b i r d s ,  118  cord i n the  ventral  1988)  and  elicits  retrograde  (True  blue,  HRP,  d e x t r a n amines) and  neuroanatomical  tracing  the medial medullary nucleus Tsai  Red  reticular  (ICo),  reticular  r o s t r a l .pontine r e t i c u l a r (Webster,  i n an  raphe  see Kuypers,  ideal position  implicate  Cnv  reticular  nucleus  (FRL,  (RPc,  include  FRM),  RPgc) and  i n motor c o n t r o l 1981)  and  output  (Garcia-Rill  sites  a g o n i s t s and  and  Skinner,  of locomotion  central  injection  nucleus  produced  behaviour  in birds  injection  of acetylcholine,  inhibitors  1987a,b)  and  of the  d i d not e l i c i t  any  unknown w h e t h e r any definitively  to that  c a r b a c h o l or  medullary locomotor  found  following  acetylcholinesterase reticular  behaviour. Although  avian afferent studies  nucleus  119  our  injection  i t i s presently  p r o j e c t i o n s t o Cnv from  Cnv  induced.  1 9 8 7 a ) . However, p i l o c a r p i n e  locomotor  cholinergic,  into  atropine-reversible  i n a manner s i m i l a r  Skinner,  acetylcholine  electrically  i n t o the cat medullary v e n t r a l  (Garcia-Rill  ventral  from t h i s r e g i o n ,  i n t o the v e n t r a l part  (Cnv)  place  motor  a n t a g o n i s t s were i n j e c t e d  f r o m w h i c h l o c o m o t i o n c o u l d be  Carbachol  afferent  f o r m a t i o n o f Noga e t a l . , 1 9 8 8 ) .  have i n t h e a c t i v a t i o n  cholinergic  TTD  cord. Hodological considerations  To examine t h e m o t o r - a s s o c i a t e d r o l e w h i c h may  of  and  t o Cnd,  as b e i n g homologous t o t h e mammalian  (magnocellular r e t i c u l a r  the  (as d i s c u s s e d  similar  and  to  more  A l l o f t h e above  to integrate  information to the s p i n a l  afferents  magnus, l a t e r a l  formation  p e r s o n a l communication).  above; f o r r e v i e w  (Cnv)  that  cerebellum, Area v e n t r a l i s  formation,  s t r u c t u r e s have b e e n i m p l i c a t e d  Cnv  formation  nucleus, nucleus  medial mesencephalic  (WGA-HRP)  t e c h n i q u e s demonstrate  intercollicularis  (AVT),  anterograde  are  laboratory point  to  several  potential  neurons  and have  from  caudal  to  nuclei been  (Rpc)  and Nucleus  as  the  in  cat  containing most  Cnv  neurons,  locomotion.  as  In  the  contain exists Kooy  formation  using  the  of  cervical  levels.  labelled  cells  of  the  medulla  implicating of  locomotion.  to  reticulospinal  (Steeves  et  et  al.  rat.  In  to  as  regions  resolve  1988).  et  al.  neurons  medial descend  arising  neurons As  to  they  shown  cervical  cholinergic  the  120  controversy  reported the  to  bird,  in  from the  neurons  the  ChAT  a  rat,  for  used  the  PPN t o  high  retrogradely formation  levels, in  possibly  the  known t o  locomotor  the  reticular  reticular  spinal  VRN a r e  no  f r o m PPN i n  demonstrated  from the  to  found  evidence  gigantocellular to  problem.  Some  also  find  descending  important in  recently  (1986),  3  elicits  G o l d s m i t h and Van Der  f r o m PPN t o  [ H]Choline  addition,  1987).  have  on  potentially  this  been  are  effect  only  projections  projection  descending  Cells  al.,  (1988)  Jones of  the  which  these  s t i l l  1987,  cholinergic  cholinergic  in  al.,  these  ChAT  and Rpc  NADPH-diaphorase histochemistry,  transport  presence  et  of  Also,  encompasses  TTD, Rgc  VRN h a v e  connections,  cholinergic  in  retrograde  (Rye  to  (MPv).  cholinergic  are  needed  PPN p r o j e c t i o n s  these  this  pathways  include,  parvocellularis  profundus  that  stimulation  Rye  have  containing  These  Cnv i t s e l f  electrical  descending  significant  pars  speculate  is  Cnv.  reticularis  1986),  these  ChAT  reticularis  to  regarding  However,  to  candidates  rat,  of  al.,  Further study  (1988),  project  Nucleus  We c a n  acetylcholine  evidence rat.  et  However,  cholinergic.  both  mesencephalicus,  (Jones  likely  to  possess  TTD, Nucleus  (Rgc),  neurons.  the  found  rostral,  gigantocellularis  which  control give  rise  control  immunoreactivity  has  been found  lateral and  tegmental  Reiner,  intrinsic output studies  i n the tegmental field  1987),  to this  and  r e g i o n may  indicate  elucidated.  t h a t i n mammals, as cholinergic  I t appears  neurons o r i g i n a t i n g are at l e a s t  the  u t i l i z e d both reticular  the  results  (Vincent  neurons (or be  however, t h a t  a v i a n Cnv,  Steeves,  chemical  t h e mammalian  locomotion  reticular  formation  i n the  investigators  cat produced  (1978) d e s c r i b e d two  w h i c h gave v e r y d i f f e r e n t first  cat  of the  nucleus,  that  pontine  electrical  (Mori et a l . , 1978).  r e s u l t s when e l e c t r i c a l l y  produces a decrease  from  postural atonia  regions i n the pontine  r e g i o n , which l a y d o r s a l l y  pontine  (1984) f o u n d  the d o r s a l aspects  i n the mesencephalic  have  o f motor r e s p o n s e s  Katayama e t al.  intact  reticular  in birds  t o t h a t seen w i t h d o r s a l m i d l i n e p o n t i n e  stimulation  VRN,  control.  s t i m u l a t i o n of the  f o r m a t i o n t o evoke a v a r i e t y  of carbachol into  be  (RP)  electrical  injection  reticular  reticulospinal  like  1987). P r e v i o u s  and  above  definitive  remain t o  s t i m u l a t i o n of the v e n t r a l pontine  region. Interestingly,  pontine  observed  b e e n shown t o e l i c i t  (Sholomenko and  in birds,  under c h o l i n e r g i c m u s c a r i n i c  R e t i c u l a r Formation  f o r m a t i o n has  The  that  inputs to the medullary  likely,  from  partially  Electrical  al.  olive)  to  n e u r o n s ) t o d e s c e n d i n g . r e t i c u l o s p i n a l n e u r o n s . The  r e s p o n s i b l e f o r the  et  (medial  provide interneuronal input  formation  similar  cat  supporting the p o s s i b i l i t y  related  this  of the  dorsal to i n f e r i o r  locomotor  Pontine  field  w i t h i n the i n hindlimb  Mori  tegmentum stimulated.  central  superior  extensor  muscle  tone  when s t i m u l a t e d . The  w i t h i n the boundaries increase  sympathetic implicated  neurons i n the  spinal  i n motor c o n t r o l  stimulation  in birds,  resulted  In b i r d s ,  o f TTD  of the nucleus  in  reticular  i n p u t from  Dubbeldam,  communication)  and  from t h e t e c t u m  efferents  brainstem  reticular  communication).  RP  W e b s t e r and supports  (Arends  cervical  funiculus  locomotion  of the  1988),  area,  from t h e  caudal cuneiform  (Garcia-Rill al.,1986). tegmental  e t al.,  It also nucleus  Injection locomotion  spinal  the  and  lower  travel  e t al.,  1982;  s t u d i e s show  1987), that  r e g i o n of the v e n t r a l  rat  to  c o r d which  (Cabot  Steeves,  Jordan,  VII,  descending  s t u d i e s demonstrate  o f c a r b a c h o l i n t o RP  or a f f e c t i n g  cord  i n t h e c a t and  i n the  197 6 ) . I t  personal  lumbar s p i n a l  receives afferent (TLD)  1982)  (Webster,  to sparse  ( S t e e v e s and  1983)  Kunzle,  Dubbeldam,  (Sholomenko and  receives projections  and  a r e g i o n which l e s i o n  Mammalian n e u r o a n a t o m i c a l  interpolaris  motor n u c l e i V and  and  and  c a u d a l i s and  (Hunt  also gives rise  Steeves,  electrical  Webster, p e r s o n a l  formation n u c l e i  p r o j e c t i o n s to both the v e n t r a l  1982;  t o c a u d a l TTD,  nucleus p a r a b r a c h i a l i s  Mori's  f o r m a t i o n i s known t o  the n u c l e i  and  projects  been  locomotion.  the pontine  afferent  on p r e g a n g l i o n i c  1982). L i k e  ventral pontine  an  birds,  have n o t  e t al.,  (Cabot  lying  magnus, p r o d u c e s  c o r d and  (Arends  in  raphe  region,  c o n n e c t i o n s a r e known t o i m p i n g e  i n cats,  receive  more v e n t r a l  i n e x t e n s o r t o n e when s t i m u l a t e d . I n  raphe-spinal  results  second  1984)  rat  RP  tegmental  and  PPN  (Garcia-Rill  et  i n p u t from t h e  laterodorsal  ( B r u d z y n s k i e t al.,  1988).  was  ineffective  at  eliciting  stimulus t h r e s h o l d necessary  to  evoke l o c o m o t i o n  i n the  r e q u i r e d to determine antagonists affect injection  be  whether c h o l i n e r g i c  locomotor  at producing  Reticular  Electrical formation,  locomotor  sites  medial mesencephalic  reticular  reticular  receives afferent  communication). and m e d u l l a r y  high c e r v i c a l personal  and  compared t h e s e  al.,  to those  FRM  2), a p o r t i o n  lateral  MLR  197 6;  cord,  as t o  1982;  ( S t e e v e s and  the  similar  e t al.  o f t h e mammalian o f which,  the  Webster,  a p p e a r t o have Cabot  dorsal  Webster,  projections to  Karten,  o f ICo.  connections to those  the  Steeves,  f o r m a t i o n , as w e l l  and  and  elicited  spinal  Kunzle,  ( R e i n e r and FRL  (FRL)  (1982) cuneiform  i n mammals, i s Jordan,  1984;  Shik  1966).  In one reduced  cord  4&5).  (Sholomenko and  and  reticular  efferents  (see C h a p t e r  b e l i e v e d t o be et  spinal  (FRM),  i n p u t from t h e  (Hunt  and  intercollicularis  I t sends e f f e r e n t  communication).  afferents  nucleus  tectum  region  reticular  formation  formation  1 9 8 8 ) . ICo  and  (Chapters  i n the nucleus  i n the decerebrate b i r d  column n u c l e i ,  antagonists  (MRF)  locomotion  pontine  r e g i o n . However,  of the mesencephalic  mesencephalic  and  changes i n t h i s  chapters  Formation  stimulation  including  lateral  personal  agonists  patterns i n this  d i s c u s s e d i n subsequent  Mesencephalic  (ICo),  p r e p a r a t i o n t e s t e d . F u r t h e r study i s  o f o t h e r n e u r o t r a n s m i t t e r a g o n i s t s and  were e f f e c t i v e will  one  o f two  birds,  the e l e c t r i c a l  This equivocal result  injection  stimulation suggests  that  of carbachol i n t o the  MRF  t h r e s h o l d f o r locomotion. detailed  study  i s required  to determine locomotor  any p o s s i b l e  role  for acetylcholine  r e g i o n . As i s d i s c u s s e d below,  b i r d may p r o v i d e i m p o r t a n t  a study  i n the  information concerning the control of  l o c o m o t i o n by t h e c u r r e n t l y locomotor  such  i n this  i d e n t i f i e d mammalian  mesencephalic  regions.  N- [ H ] m e t h y l s c o p o l a m i n e b i n d i n g s t u d i e s i n t h e b i r d 3  the presence but  little  of muscarinic cholinergic  binding i n either  ChAT i m m u n o h i s t o c h e m i c a l  r e c e p t o r b i n d i n g i n ICo  FRL o r FRM  (Dietl  s t u d i e s demonstrate  e t a l . , 1988).  s p a r s e o r no  labelling  of potential  cholinergic  cells  (Taccogna  and Steeves,  unpublished  o b s e r v a t i o n s ) , thus  any  homology between t h e s e m i d b r a i n  ACh-containing Garcia-Rill  cell  bodies  and co-workers  Interestingly,  of acetylcholine  eliciting  locomotion  al.  locomotion  structures  (Garcia-Rill  regions negating  and t h e  e t a l . , 1983a).  e t a l . (1985) f o u n d  that  i n t o t h e PPN/MLR was i n e f f e c t i v e a t  i n the decerebrate  (1988) f o u n d t h a t  i n these  o f t h e mammalian PPN/mMLR d e f i n e d by  Garcia-Rill  injection  show  c a t and B r u d z y n s k i e t  carbachol injection  i n t h e f r e e l y moving i n t a c t  i n t o PPN d e c r e a s e d  r a t . However, c a r b a c h o l  i n j e c t i o n s p l a c e d between t h e PPN, c u n e i f o r m n u c l e u s a n d periaqueductal equivalent  possibly within the region of the r a t  o f t h e c a t 1MLR, i n c r e a s e d l o c o m o t i o n  (Brudzynski The  gray,  e t a l . , 1988).  above r e s u l t s  i n c a t and r a t appear t o l e n d credence t o  t h e e x i s t e n c e o f two MLRs, e a c h characteristics injection  i n the r a t  possessing  t h a t may be more f u l l y  studies.  different  d e f i n e d by  neurochemical  The p h a r m a c o l o g i c a l p r o p e r t i e s o f n e u r o n s i n  corresponding anatomical  structures  i n the midbrain  o f b i r d s and  mammals  indicate  that  different populations  somewhat d i f f e r e n t c o n t r o l active  i n the control  regions the  mechanisms, b u t a r e b o t h  intercollicularis  p r o p o s e d as t h e l a t e r a l studies  are required,  apparently  o f l o c o m o t o r b e h a v i o u r s . We s u g g e s t  i n the avian midbrain,  nucleus  o f neurons a r e under  specifically  that  i n the regions of  a n d mMRF, a r e e q u i v a l e n t  a n d m e d i a l MLRs o f mammals.  t o those  Further  however, b e f o r e any homology between t h e  mammalian a n d a v i a n MLRs c a n be c o m p l e t e d .  Medial Longitudinal  Fasciculus  L o c o m o t i o n was e l i c i t e d pontine  locomotor The  i n j e c t i o n i n t o t h e MLF e l i c i t e d  from a l l v e s t i b u l a r  1983),  1984),  inferior  ofthe  fasciculus similar  nuclei  n u c l e u s o f C a j a l (InC)  1983). I t c a r r i e s  f i b r e s f r o m t h e 1) cord  ( C a r p e n t e r and  2) InC, w h i c h forms t h e i n t e r s t i t i o - s p i n a l t r a c t 1983), t o t h e P r o b s t ' s t r a c t  3) r o s t r a l b r a i n s t e m  o l i v a r y nucleus  1984)),  ascending  t o v i s u a l motor  r e t i c u l a r formation t o the spinal  ( C a r p e n t e r and S u t i n ,  al.,  nuclei  t o the i n t e r s t i t i a l  (Carpenter and S u t i n ,  al.,  longitudinal  MLF i s a f i b r e t r a c t w h i c h c a r r i e s  projections  pontine  stimulation  patterns.  projections  Sutin,  by e l e c t r i c a l  and r o s t r a l m e d u l l a r y m e d i a l  (MLF). C a r b a c h o l  and  (MLF)  (Carpenter and S u t i n ,  4) v e s t i b u l o s p i n a l  the  medullary  and  5) i n t e r n u c l e a r  ( e . g . InC) n u c l e i  to the  1983; S k i n n e r e t  t r a c t which sends c o l l a t e r a l s t o  r e t i c u l a r formation  (Carpenter and S u t i n ,  v i s u a l motor n u c l e i  (Carpenter and S u t i n ,  (Skinner et  1983). In a d d i t i o n ,  1983)  ( I I I , IV a n d V I ) t h e MLF c a r r i e s  fibres  w h i c h i m p i n g e on t h e p e d u n c u l o p o n t i n e n u c l e u s unspecified)  this  i t was n o t s u r p r i s i n g t h a t  tract  elicited  nuclei,  neurochemical  carbachol  lasting  although  positively region et  To o u r  have b e e n r e p o r t e d  i n the  stain  f o r a c e t y l c h o l i n e s t e r a s e have b e e n l o c a l i z e d a n d duck  a l . , i n preparation) of these  locomotor  the c h o l i n e r g i c agonist  s e r o t o n i n - c o n t a i n i n g neurons which  i n the chicken  features  reticular  i t was s u r p r i s i n g  locomotor behaviours.  knowledge, no c h o l i n e r g i c r e c e p t o r s MLF,  (e.g. p o n t i n e  pedunculopontine nucleus),  long  stimulation of  a s many o f i t s f i b r e  function  stimulation with  elicited  electrical  locomotor responses,  are r e l a t e d t o locomotor  formation that  (Rye e t al., 1 9 8 7 ) .  While  tracts  i n t h e r a t (source  (Dube and P a r e n t ,  in  this  1981; T a c c o g n a  (see C h a p t e r 2 ) . The h o d o l o g i c a l  n e u r o n s and t h e i r p o s s i b l e r e l a t i o n t o  f u n c t i o n , however, r e m a i n t o be d e t e r m i n e d .  PHARMACOLOGICAL CONSIDERATIONS  Neurochemical regions  This  c a n be a c h i e v e d  ionophore or i n d i r e c t l y  agonist  neurotransmitter  (muscarinic  neurochemical  i s d e p e n d e n t upon t h e a g e n t  are b e l i e v e d t o induce  proteins.  contain  The mode o f a c t i o n by w h i c h t h e  the receptor  Agonists  regions  locomotor  w h i c h c a n be a f f e c t e d by c h o l i n e r g i c a g o n i s t s and  antagonists.  system  i n t o some o f t h e above  demonstrated that these  receptors  affects  injection  conformation  utilized.  changes i n r e c e p t o r  through d i r e c t  coupling to the  v i a a c t i v a t i o n o f a second messenger  receptors  - see Buckley  p r e s u m a b l y p r o d u c e s an a l t e r a t i o n  e t al., 1 9 8 8 ) . The i n the ionic  permeability  o f t h e membrane,  which e l i c i t s  leading t o a neuronal  downstream r e s p o n s e s  response  (e.g. locomotion).  Antagonists,  on t h e o t h e r hand, a r e b e l i e v e d t o f o r m an i n e r t  complex w i t h  t h e r e c e p t o r p r o t e i n , which,  competitive  antagonist,  at s p e c i f i c  binding  s t u d i e s , s e e Watson e t al.,  by  the injected  activation block)  concentrations  locomotion  neurochemical t o  of competitive  1984).  t h e r e c e p t o r s , when a c t i v a t e d o r i n a c t i v a t e d  or block  (or blockade)  inactivating  (for review  agent, presumably a f f e c t  neurons t o e l i c i t  decerebrate  i s dependent spread  receptors)  a sufficient  avian  on t h e a b i l i t y  through the t i s s u e until  signs o f locomotion  ENGs. Thus,  neurochemicals  t o evoke (or of the  r e c e p t o r s (and  so t h a t t h e o u t w a r d  c a n be r e c o r d e d  with  which a r e not r e a d i l y  than  t o counteract  (e.g. c a r b a c h o l ) affinities  the effects  [atropine»>carbachol  the concentration  the  same  s u c h as a c e t y l c h o l i n e  o f one  neurochemical  o f another  i s d e p e n d e n t upon t h e i r  and  o f each agent,  neurochemical  relative  (Furchgott  (e.g.  binding  and Cherry,  i f the pair  1984)]  are acting at  site.  In t h e c a s e this  neurochemicals  1985). A l s o , t h e a b i l i t y  atropine)  carbachol  be more e f f e c t i v e s t i m u l a t o r s / i n h i b i t o r s  r e a d i l y metabolized  (Taylor,  EMGs o r  metabolized  [ e . g . a c e t y l c h o l i n e s t e r a s e w h i c h does n o t h y d r o l y z e 1985)] w i l l  The  (activating or  enough n e u r o n a l  behavioural  number o f  locomotion.  o f neurons necessary  t h e r e f o r e n e u r o n s ) have b e e n r e c r u i t e d  (Taylor,  of a  c a n be d i s p l a c e d by an a p p r o p r i a t e  agonist  In my s t u d y ,  i n t h e case  study,  of the carbachol  versus  atropine mainly  a t r o p i n e h a s b e e n shown t o d i s p l a c e r e c e p t o r  127  used i n bound  carbachol  (and p i l o c a r p i n e ) a t m u s c a r i n i c  1985). Recent the  findings  competitive  (Christie  receptors  and North,  antagonism o f c a r b a c h o l  (Taylor,  1988) s u g g e s t  by a t r o p i n e a t  muscarinic  receptors  i s not d i r e c t l y  muscarinic  receptors  l o c a t e d d i s t a n t t o the ionophore  and  1988). While  North,  nature  being  s t i m u l a t e d by t h e  this  of the locomotion-associated  neurochemical  that muscarinic  pharmacological  however, w i t h o u t injection  locomotion readily  technique. I t  c a n be i m p l i c a t e d i n  o f locomotion  First,  modified  i ti s d i f f i c u l t  by  neurochemical  as i s e l e c t r i c a l  Third, like  electrical  neurochemical,  intracerebrally  stimulation, the lack of a  neurochemical may  physiological, recruit  although  a sufficient  necessary  (see b e l o w ) . F i f t h ,  injected  neurochemicals  reflect  the concentrations of are probably not i n order t o  provides  no i n f o r m a t i o n  concerning  location  of the receptors. Lastly, that the  locomotion, i t  physiological concentration at  injection point. Sixth, the intracerebral  for the p o s s i b i l i t y  the spread o f  distribution, i s  number o f n e u r o n s t o e l i c i t than  the efficacy of  Fourth,  i t may be a r g u e d t h a t  t o use higher  Second, t h e  stimulation-induced  and t h e r e f o r e , e f f e c t i v e  to control  to titrate  s t i m u l a t i o n i s n o t as  the p r e p a r a t i o n a t t h e time o f i n j e c t i o n .  difficult  i s not,  dose t o produce t h r e s h o l d a c t i v a t i o n .  r e s p o n s e t o any g i v e n  the  (Christie  c h o l i n e r g i c receptors  injection  receptors  activation  limitations.  elicited  locomotion.  is  b u t on  control. The  the  on t h e i o n o p h o r e ,  i t i s not y e t p o s s i b l e t o determine t h e  exact  appears l i k e l y  that  the pre-  technique  or post-synaptic  the technique  neurochemical 128  infusion  cannot  i s activating  account  receptors present  on n e u r o n s w h i c h n o r m a l l y  have no a f f e r e n t  i n p u t s a s s o c i a t e d w i t h t h a t t r a n s m i t t e r a n d w h i c h may n o t normally  be i n v o l v e d i n t h e l o c o m o t o r  process  cholinergic  r e c e p t o r may be p r e s e n t  cholinergic  i n p u t , a l s o see Stone and Burton,  The its  limitations  usefulness  of this  technique  i n demonstrating  electrophysiologically-defined neuronal  receptors  on a c e l l  concerning  possible neurotransmitter  evoked  provides  predictive value  infusion  information  i d e n t i f i e d with  c o u l d be e x a m i n e d u s i n g  Freed,  in-vivo  c o n t r o l . The a l s o has F o r example,  neurochemical  m i c r o d i a l y s i s (Sabol  1988; B e c k e r e t a l . , 1988; A j i m a a n d K a t o , 1988;  e t a l . , 1 9 8 8 ) . The d i a l y s i s  quantify  the release of neurotransmitters  locomotion  inputs t o the  i n determining the  technique  Phillips  role  locomotor  f o r t h e use o f other techniques.  prospective neurotransmitters infusion  also contain  controlling  and has p r e d i c t i v e v a l u e  neurochemical  preclude  somal o r on t e r m i n a l s )  o f n e u r a l pathways i n v o l v e d i n locomotor  intracerebral  and  regions  (presumably d e n d r i t i c ,  Further, the technique  nature  1988).  do n o t , however,  locomotor  responses.  regions  w h i c h h a s no  that the  w h i c h may u n d e r l i e t h e p h y s i o l o g i c a l l y  locomotor  (e.g. a  and thereby  i n brainstem  technique  may be u s e d t o  during  evoked  e l u c i d a t e w h i c h n e u r o t r a n s m i t t e r s have a  locomotor  control.  NEUROCHEMICAL SPREAD AND TIME COURSE OF ACTIVATION/INACTIVATION  Although (Chapters  this  study  and those  i n the f o l l o w i n g chapters  4 & 5) d i d n o t i n c l u d e t h e i n j e c t i o n  129  o f dye m a r k e r  chemicals  i n t o t h e i n j e c t i o n s i t e s t o mark t h e degree o f  neurochemical  spread,  i t i s l i k e l y that the s i z e o f our  s t i m u l a t i o n s i t e s were s m a l l e r t h a n t h o s e shown i n t h e c a t ( G a r c i a - R i l l e t al., 1985, G a r c i a - R i l l and S k i n n e r , slow i n j e c t i o n r a t e used i n t h e p r e s e n t  study  1987). The  (0.2/il/min) , as  compared t o t h a t u t i l i z e d by o t h e r g r o u p s ( e . g . G a r c i a - R i l l e t al.,  1985 - 1/il/min; G a r c i a - R i l l and S k i n n e r ,  1987a - 1/jl/min;  Noga e t al., 1988 - l j i l / m i n ; L a i and S i e g e l , 1988 - 0.5nl/min) and t h e s m a l l volumes (maximum l.Ofil) as compared t o o t h e r s (e.g. G a r c i a - R i l l e t al., 1985 - 1.5-3.0jxl; Noga e t a l . , 1988 5/il (see Appendix I ) ) i n j e c t e d would have s e r v e d t o reduce t h e neurochemical  spread t h r o u g h t h e t i s s u e . A l s o , a f f e c t e d areas  were p r o b a b l y  w i t h i n <0.5mm r a d i u s , f o r i t was n o t e d i n s e v e r a l  t r i a l s o f the present  study t h a t i n f u s i o n o f a  neurochemical  0.5mm from an e f f e c t i v e s i t e d i d n o t e l i c i t l o c o m o t i o n . u t i l i z i n g autoradiographic t r a c i n g of dispersed s i l v e r  Studies grains  f o l l o w i n g i n j e c t i o n o f r a d i o a c t i v e a g o n i s t s and a n t a g o n i s t s  into  i n j e c t i o n s i t e s might s e r v e t o c o n f i r m t h e degree o f spread after intracerebral infusion of  neurochemicals.  With regard t o the l a t e n c y f o r a c t i v i t y o f the various neurochemicals  u t i l i z e d , t h e r e appears t o be a g e n e r a l  that small molecular ( m o l e c u l a r weight 103.1) (Chapter  weight n e u r o c h e m i c a l s  trend  (e.g. c a r b a c h o l  (MW) = 1 8 2 . 6 ) ( t h i s c h a p t e r ) , GABA (MW =  4) and NMDA (MW = 147.1) (Chapter  q u i c k l y than those w i t h l a r g e molecular  weight  5)) a c t e d more (e.g. a t r o p i n e  (MW = 6 7 6 . 8 ) ( t h i s c h a p t e r ) , p i c r o t o x i n (602.6)(Chapter 4 ) ) . Whether t h i s t r e n d r e s u l t s from a d i f f e r e n t i a l d i f f u s i o n r a t e t h r o u g h t h e t i s s u e s remains t o be d e t e r m i n e d . A l s o , t h e time 130  course  (see T a b l e  maintained those  their  1) o v e r w h i c h t h e a g o n i s t s a n d a n t a g o n i s t s locomotor  nucleus  atropine injection (NRV - s e e A p p e n d i x  stimulation-induced Skinner,  formation least  t o be s i m i l a r t o  (see A p p e n d i x  the cat ventral  f o r 1-2 h o u r s  For  reticular  study,  ( G a r c i a - R i l l and  atropine injection  region, the ventral  i n t o an  reticular  (Cnv), b l o c k e d e l e c t r i c a l l y s t i m u l a t e d l o c o m o t i o n f o r the length of the experimental period t o produce  cat, although differences  COMPARATIVE  The  I).  I) blocked e l e c t r i c a l  i n this  avian brainstem  a t r o p i n e appears  to  into  locomotion  1987a), w h i l e  equivalent  and  appeared  r e p o r t e d by o t h e r i n v e s t i g a t o r s  example,  at  effects  long l a s t i n g  i ti s difficult  i n both  (21-40min).  effects  i n both  Thus,  bird  t o compare t h e s e e f f e c t s due  c o n c e n t r a t i o n and i n j e c t i o n  volume.  CONSIDERATIONS  neuroanatomical  and n e u r o p h y s i o l o g i c a l comparison  of  b i r d s w i t h mammals i s somewhat h i n d e r e d b y t h e d i f f e r e n t neuroanatomical appears is  that  terminology  f o r t h e two g r o u p s .  neural c i r c u i t r y i n the b i r d midbrain  comparable t o t h a t  diverging  used  o f mammals  and h i n d b r a i n  ( R e i n e r e t a l . , 1984),  a t t h e l e v e l o f t h e output  the b i r d  a p p e a r t o be f u n d a m e n t a l l y  mammals  (Cabot  results,  that  cholinergic brainstem  stimulation  r e g i o n s produce  both  e l e c t r i c a l and  avian locomotion,  1 9 8 8 ) . My  neurochemical  (carbachol, pilocarpine)  131  pathways  comparable t o those o f  e t a l . , 1982; W e b s t e r a n d S t e e v e s , demonstrate  only  of the basal ganglia  (Reiner e t a l . , 1984). A l s o , t h e h i n d b r a i n d e s c e n d i n g in  However, i t  of restricted  are similar  t o those  brainstem  regions  i n mammals. T h e s e s i m i l a r i t i e s  underscore the  suggestion  underlying  c o n t r o l of locomotion  these  the  neuroanatomical  hindbrain  although  our  are under c h o l i n e r g i c m u s c a r i n i c  elucidated.  132  substrate  for  results  several locomotion-promoting regions  the p r e c i s e neuroanatomical  r e m a i n s t o be  substrate  i s highly conserved  groups of v e r t e b r a t e s . Furthermore,  demonstrate t h a t avian  t h a t the  therefore  in  the  control,  for this  control  CHAPTER 4 CHARACTERIZATION OF AVIAN MID- AND HINDBRAIN SITES THAT PRODUCE LOCOMOTION WITH INTRACEREBRAL INFUSION OF NEUROTRANSMITTER AGONISTS AND  ANTAGONISTS  (II) : r-AMINOBUTYRIC ACID (GABA)  133  INTRODUCTION  In v e r t e b r a t e s , t h e c o n t r o l o f locomotor b e h a v i o u r i s dependent upon c e n t r a l nervous  system  (CNS)  c i r c u i t r y at a l l  l e v e l s o f t h e n e u r a x i s . Attempts t o c h a r a c t e r i z e t h i s  circuitry  p h y s i o l o g i c a l l y have u t i l i z e d a v a r i e t y o f t e c h n i q u e s i n c l u d i n g a b l a t i o n , s e l e c t i v e l e s i o n s , e x t r a - and i n t r a c e l l u l a r r e c o r d i n g , e l e c t r i c a l stimulation and S h i k , 1976)  ( f o r r e v i e w see G r i l l n e r , 1975;  Orlovsky  and more r e c e n t l y , neurochemical s t i m u l a t i o n 1985; Noga e t al.,  (Garcia-Rill et a l . ,  Steeves, 1987a). N e u r o a n a t o m i c a l  1988;  Sholomenko and  s t u d i e s have p r o v i d e d v a l u a b l e  i n f o r m a t i o n r e g a r d i n g t h e o r i g i n , c o u r s e and t e r m i n a t i o n s o f CNS n u c l e i thought t o be i n v o l v e d i n l o c o m o t i o n H o l s t e g e and Kuypers, G a r c i a - R i l l e t al.,  1987;  (Kuypers, 1981;  Steeves and J o r d a n , 1984;  1983a). Recent s t u d i e s have a i d e d i n t h e  i d e n t i f i c a t i o n and l o c a l i z a t i o n o f n e u r o t r a n s m i t t e r s and t h e i r r e c e p t o r s which may be i n v o l v e d i n t h e locomotor p r o c e s s  (e.g.  Mugnaini and O e r t e l , 1985). The p r e s e n t s t a t e o f knowledge, t h e r e f o r e , a l l o w s f o r t h e i n i t i a t i o n o f an i n t e g r a t e d t o t h e study o f locomotor  approach  control.  The p r e v i o u s c h a p t e r (Chapter 3) t a k e s t h i s approach i n t h e d e s c r i p t i o n o f t h e locomotor e f f e c t s o f c h o l i n e r g i c a g o n i s t and a n t a g o n i s t i n j e c t i o n s i n t o s i t e s i n t h e a v i a n mid- and h i n d b r a i n . R e s u l t s from t h a t study demonstrated  that cholinergic  m u s c a r i n i c a g o n i s t s t i m u l a t i o n o f a v a r i e t y o f locomotor i n the h i n d b r a i n o f the decerebrate b i r d  (Canada goose o r P e k i n  duck) evoked locomotor b e h a v i o u r s . Furthermore,  attempts were  made t o e l u c i d a t e t h e c h o l i n e r g i c s u b s t r a t e i n v o l v e d i n 134  sites  locomotor  control  vertebrates. injection  This chapter  into these  r e g i o n s as a p r e l u d e  acid  effects of  (GABA), i t s a g o n i s t s a n d  same s i t e s .  whether GABAergic  f i n d i n g s t o other  d e s c r i b e s t h e locomotor  o f y-aminobutyric  antagonists survey  and g e n e r a l i z e these  The s t u d y  was d e s i g n e d t o  neurochemicals were e f f e c t i v e  t o more d e t a i l e d  i n these  pharmacological  characterization. S i n c e t h e d i s c o v e r y o f GABA by two i n d e p e n d e n t g r o u p s i n 1950 ( R o b e r t s  and F r a n k e l ,  research  1950), GABA h a s b e e n w e l l c h a r a c t e r i z e d a s a r a t h e r inhibitory  n e u r o t r a n s m i t t e r which a c t s both  postsynaptically the  (Olsen,  cat (Garcia-Rill  Noga e t al.,  1981; Bloom,  e t al.,  into  s e l e c t e d locomotor  p r e - and  1985). Recent  e t al.,  behaviour  regions  In t h e b i r d , locomotion effective  i n these  of the neuraxis,  1985;  infusion  while  injection  or increase  preparations.  GABA i n j e c t i o n  into  sites  c o u l d be e l i c i t e d b y e l e c t r i c a l  from  which  s t i m u l a t i o n was  at blocking or increasing the threshold f o r  electrically  stimulated locomotion  preparation.  I n a d d i t i o n , GABA a n t a g o n i s t s e l i c i t e d  when i n j e c t e d  into  neurochemicals  some o f t h e s e  i n the decerebrate  same s i t e s .  locomotion  Because t h e  i n f u s e d a r e b e l i e v e d t o a c t on n e u r o t r a n s m i t t e r  receptors  ( G o o d c h i l d e t al.,  locomotor  sites  are  studies i n  1988) have  c a n be b l o c k e d b y GABA  o f GABA a n t a g o n i s t s h a s b e e n shown t o i n d u c e locomotor  ubiquitous  1985, 1987; E l d r i d g e e t al.,  1988) a n d r a t ( B r u d z y n s k i  demonstrated that locomotion  al.,  1950; Awapara e t  1982),  contain neuronal  i n v o l v e d i n t h e locomotor  i ti s likely  populations  process.  135  that  these  or terminals  Our r e s u l t s  which  i n the bird  are  similar  1985,  t o those described  1987; Noga e t al.,  contention hindbrain  that  avian  levels,  1988) CNS  f o r mammals  (Garcia-Rill  and t h e r e f o r e  underlie  motor c i r c u i t r y , a t l e a s t  i s homologous t o t h a t  136  o f mammalian  et a l . ,  our  a t m i d - and species.  MATERIALS AND METHODS  The m a t e r i a l s procedure, injection  including the decerebration  e l e c t r i c a l s t i m u l a t i o n methodology, p a r a m e t e r s and h i s t o l o g i c a l  localization in  a n d methods,  of stimulation  sites  C h a p t e r s 2 & 3.  137  neurochemical  procedures  for the  have b e e n p r e v i o u s l y  described  RESULTS  GABA A g o n i s t s  and A n t a g o n i s t s  Introduction into e l e c t r i c a l l y hind-  o f GABA,  stimulated locomotion  and m i d b r a i n  variety  were e f f e c t i v e  o f locomotor p a t t e r n s  neurochemicals  injected  non-competitive agonist  and; b i c u c u l l i n e ,  concentration  a  b i r d s . The  picrotoxin, a  muscimol,  a GABAA  receptor  a GABAA r e c e p t o r  competitive  injection  t h e lowest  and time course  i n the  sites,  of activity  are l i s t e d  effective i n Table  2  d e s c r i b e d i n t h e t e x t . A composite diagram o f t h e i n j e c t i o n  sites  i s shown i n F i g u r e 15.  Pontobulbar  Five  L o c o m o t o r S t r i p (PLS)  o f e i g h t animals  (3-20mM/l. Ojil) patterns.  which r e c e i v e d p i c r o t o x i n i n j e c t i o n s  i n t o PLS p r o d u c e d l o n g l a s t i n g  The mean l a t e n c y t o o n s e t  initial  i n j e c t i o n was 13.5 m i n u t e s  periods  of activity  point of  promoting s i t e s  i n decerebrate  GABA a n t a g o n i s t ;  and a n t a g o n i s t s  a t b l o c k i n g and e l i c i t i n g  i n c l u d e d : GABA;  antagonist. Neurochemical  and  o r GABAergic a g o n i s t s  flying  f o r locomotion (range  alone.  picrotoxin  included walking In three b i r d s ,  injection  following the  4-22 m i n u t e s ) w i t h t h e  l a s t i n g between 35 and 60 m i n u t e s  t h e e x p e r i m e n t was t e r m i n a t e d ) .  locomotion  locomotor  alone,  The s i t e - d e p e n d e n t running  the i n i t i a l  stepping  138  modes  a n d f l y i n g , and  locomotor r e a c t i o n t o  involved small u n i l a t e r a l  (similar to the b i l a t e r a l  (at which  elicited  l e g excursions  at threshold  TABLE 2 GABAergic agonists and antagonists Animal  Site  Chemical  TTD  Cnd Cnv  Concentration* Injected  Lowest Volume Effective Concentration  GABA 7.2-7.4 Picrotoxin " Bicuculline " Muscimol "  0.3-O.SM 3-20mM 10mM 6.5-25mM  0.3M 3mM 10mM 6.5mM  Picrotoxin Muscimol  " "  SmM 6.25mM  none none  GABA Picrotoxin Muscimol  O.SM 6-20mM 6.25mM  0.5M SmM 6.2SmM  ••  " "  "  M  O.SM 3-SmM 6.25mM  0.6M SmM none  »  ••  0.6M 5-20mM  0.6M SmM  ••  GABA Picrotoxin Muscimol  RP  MRF  GABA Picrotoxin  pH  "  "  ABBREVIATIONS: Cnd Cnv MRF RP TTD  — — — — —  dorsal part, medullary central nucleus ventral part, medullary central nucleus mesencephalic reticular formation pontine reticular nucleus descending trigeminal tract and nucleus  139  I.Oul  Rale  Time Course (min) Latency Period  0.2ul/min  1-5 4-22 15 6-10  2-21 35-60 >30 30-70  ••  none none  none none  ••  <1 4-22 >B  0-14 30 >30  «1 10  12-21 35  —  —  "  " "  •' *'  "  ••  "  <1 11-13  2-12 >30  Figure  15. C o m p o s i t e d i a g r a m o f G A B A e r g i c a g o n i s t a n d a n t a g o n i s t  neurochemical through left  injection  various levels  sites.  of the avian neuraxis  c o r n e r o f each l e v e l ,  illustrates brainstem electrical (filled  t h e locomotor  regions  from  The d i a g r a m o f c o r o n a l s e c t i o n s  A=anterior, effects  s t i m u l a t i o n . Where GABA  circle)  P=posterior  o f each  which locomotion  was f i r s t  their  ( i n mm)]  neurochemical  (filled  a r e shown a s f i l l e d ,  [numbers i n u p p e r  in  e l i c i t e d by  square) and muscimol e f f e c t s were t o b l o c k  locomotion. Key  A b b r e v i a t i o n s : BICUC - b i c u c u l l i n e ,  acid,  GABA -  MUSC - m u s c i m o l , PICRO - p i c r o t o x i n ;  (except  f o r GABA a n d m u s c i m o l ) ,  LOCO -  TH - d e c r e a s e d  threshold  intensity  f o r locomotion,  threshold  intensity  f o r locomotion,  t  y-aminobutyric  electrical  TH - increased NR - no  locomotion  electrical  response.  A b b r e v i a t i o n s : BC - b r a c h i u m c o n j u n c t i v u m , CC - c e n t r a l c a n a l , Cnd - c e n t r a l n u c l e u s m e d u l l a , d o r s a l p a r t , Cnv - c e n t r a l n u c l e u s m e d u l l a , v e n t r a l p a r t , EW - E d i n g e r W e s t p h a l n u c l e u s , I I I - o c c u l o m o t o r n u c l e u s , 10 - i n f e r i o r o l i v a r y n u c l e u s , IP n u c l e u s i n t e r p e d u n c u l a r i s , LC - l o c u s c o e r u l e u s , MLd - l a t e r a l m e s e n c e p h a l i c n u c l e u s , d o r s a l d i v i s i o n , MLF - m e d i a l l o n g i t u d i n a l f a s c i c u l u s , MRF - m e d i a l m e s e n c e p h a l i c reticular f o r m a t i o n , MV - t r i g e m i n a l m o t o r n u c l e u s , N IV - t r o c h l e a r n e r v e , N X I I - h y p o g l o s s a l n e r v e , OT - o p t i c tectum., R - r a p h e n u c l e u s , RP - n u c l e u s p o n t i n e r e t i c u l a r f o r m a t i o n , Rpc - p o n t i n e p a r v o c e l l u l a r r e t i c u l a r n u c l e u s , RPO - n u c l e u s r e t i c u l a r i s p o n t i s o r a l i s , Ru - r e d n u c l e u s , SSP - s u p r a s p i n a l n u c l e u s , SO s u p e r i o r o l i v a r y n u c l e u s , ST - s u b t r i g e m i n a l n u c l e u s , SV t r i g e m i n a l s e n s o r y n u c l e u s , TPc - s u b s t a n t i a n i g r a , TTD t r i g e m i n a l d e s c e n d i n g t r a c t and n u c l e u s , VeL - l a t e r a l v e s t i b u l a r n u c l e u s , VeM - m e d i a l v e s t i b u l a r n u c l e u s , V I a b d u c e n s n u c l e u s , X - d o r s a l motor n u c l e u s v a g u s .  140  LDCO JTH TTH IR PIBB  A  A  A  A  m  •  B  B  •  HBC  •  © e o  BIQJC • • • O  141  electrical bilateral  s t i m u l a t i o n as  t r e a d m i l l stepping  progressed.  and  ( F i g . 16B)  i n the  stimulation  i n t e n s i t y was  was  17A,  (13A). One  animal,  displayed only and  bilateral  as has  included  any  picrotoxin-induced  trigeminal the  field  surface  intensity  of the  flying  (TFS)  head near the  TFS  of both  wings  This of  animals.  appeared to  before to  the  onset  i n j e c t i o n was  increase  of  stroking  increase  the  loud noise  the  Thus,  locomotion,  ineffective  short bouts of walking  flying.  at or  locomotion  force of walking  from w a l k i n g t o  stimulation,  or  performed.  after picrotoxin-induced  seemed t o  would cause a c o n v e r s i o n mechanical  group,  (either a i r puffs  eyes)  would e l i c i t  behaviour. Also, TFS  stimulation  locomotion  locomotor behaviour being  locomotion,  established,  electrical  i n the  alone  above p i c r o t o x i n - s t i m u l a t e d b i r d s ,  s t i m u l a t i o n , which p r i o r  eliciting  bird  17B,  i n s e v e r a l of the  a f t e r p i c r o t o x i n i n j e c t i o n but this  threshold.  seen a f t e r a p r o l o n g e d p e r i o d  stimulation  of the  electrical  i n one  (Fig.  (convulsant-like)  locomotion  four of the  from  d i s c r e t e l o c o m o t o r movements.  behaviour resembled that  In  leg extension  been seen d u r i n g  not  walking  i n a second, wing f l a p p i n g  t o n i c extension  legs without  increased  the  locomotor  e l i c i t e d walking alone  p i c r o t o x i n ) , while  bicuculline),  into  between  change i n  time  bilateral  s e e n i n t h e s e a n i m a l s as  gradually  injection  observed with  stronger  transition  normal animal. T h i s  s i m i l a r to that  GABA a n t a g o n i s t  then  by  i n f o r c e as  a l s o became i n c o r p o r a t e d  p a t t e r n was  (Fig.  weak and  i n a manner s i m i l a r t o t h e  flying  followed  which i n c r e a s e d  In t h e s e a n i m a l s ,  wing f l a p p i n g behaviour  s e e n i n F i g . 16A)  or  Similar to  would o c c a s i o n a l l y  was  the  elicit  Figure  16.  activity  Electromyographic records  elicited  injection  and  stepping left  f l e x o r muscle)  electrical  i n t o t h e same s i t e . of the r i g h t  two  t h e major  traces  The  t o p two  (RPECT) and wing  143  from t h e  muscles  traces left  right  (major h i p  o f t h e PLS.  injection  B:  of  illustrate  the  (LPECT)  depressors used  a r e f r o m t h e l e g ITC  A.  ( P L S ) . A:  patterns  by  locomotor  picrotoxin  stimulation  f l a p p i n g EMGs e l i c i t e d  p e c t o r a l i s muscles, bottom  r e p r e s e n t e d by EMG  e l i c i t e d by  in-phase a c t i v i t y  The  and  (LITC) i l i o t i b i a l i s c r a n i a l i s  S t e p p i n g and w i n g picrotoxin  stimulation  i n t o the pontobulbar locomotor s t r i p  Alternating (RITC)  by e l e c t r i c a l  (EMGs) s h o w i n g  for flight.  f l e x o r muscles  as i n  A RITC M H i I M I  LITC  I M | M  t >*  1MM«M<MMMMMi 3 sec  144  Figure  17.  activity the  Electromyographic records  elicited  pontobulbar  by p i c r o t o x i n  locomotor  r e p r e s e n t e d by EMG iliotibialis into the by  t h e PLS.  right.(RPECT)  and b i c u c u l l i n e  strip  Simultaneous and  left  i n j e c t i o n of b i c u c u l l i n e  locomotor  injection  into  ( P L S ) . A: A l t e r n a t i n g s t e p p i n g  p a t t e r n s from r i g h t  c r a n i a l i s muscles B:  (EMGs) s h o w i n g  (RITC) and  elicited  left  by p i c r o t o x i n  (LITC) injection  (in-phase) wing f l a p p i n g  (LPECT) p e c t o r a l i s i n t o t h e PLS  145  muscles  EMGs f r o m elicited  of a d i f f e r e n t  animal.  146  bouts  o f locomotor GABA  rapidly (2-21  activity  i n these  (0.3-0.5M) i n f u s e d  (mean <1.5 m i n u t e s ;  minutes;  locomotion activity)  range  infusion  decayed  immediately  with time  such t h a t  similar to that  I n two b i r d s  electrical  stimulation  reversibly  electrical  locomotor  stimulation  at e l i c i t i n g  (mean 10.7 m i n . ) ,  the e l e c t r i c a l  t h e b l o c k a d e wore o f f  s e e n p r e v i o u s t o GABA  injection  i n w h i c h l o c o m o t i o n was p r o d u c e d by a l o n e , GABA i n j e c t i o n  increased threshold  i n t e n s i t y maximum  f o r locomotor  ( F i g . 18A,B). The G A B A - i n d u c e d  p o s t - i n j e c t i o n was i n e f f e c t i v e  activity  blocked  stimulation or  f o r locomotion decreased u n t i l  returned.  and  threshold  (N=7)  transiently  and r e v e r s i b l y  electrical  l o c o m o t i o n . However, o v e r t i m e  and  1-5 m i n u t e s ) ,  mean 10.7 m i n u t e s )  e l i c i t e d by e i t h e r  threshold  a l l animals t e s t e d  (or i n c r e a s e d e l e c t r i c a l  picrotoxin blockade  into  animals.  (170/iA)  from  replicably  above t h e s t i m u l a t i o n  a pre-injection  50(LLA. I n t h e s e a n i m a l s ,  the reversible  e f f e c t s were s e e n  3 trials  after  (0.5M)  t h r e s h o l d mean o f  n a t u r e o f t h e GABA  o f GABA i n f u s i o n  (GABA  injection  f o l l o w e d by r e c o v e r y ) , i n which t h e e l e c t r i c a l  threshold  required to i n i t i a t e  pre-GABA v a l u e s activity  locomotion r e t u r n e d t o near  (70LLA) . I n t h r e e b i r d s ,  the tonic  extensor  w h i c h was e v i d e n t a f t e r t h e p r o l o n g e d  picrotoxin-induced  locomotion or the extensor  hypertonicity  described  above d i s a p p e a r e d f o r s h o r t p e r i o d s f o l l o w i n g  injection  into these s i t e s .  off,  locomotor  movements r e a p p e a r e d  extensor hypertonicity Muscimol,  A s t h e GABA b l o c k a p p e a r e d  the  reasserted  GABAA  agonist 147  fora brief period  GABA t o wear before  itself. (6.5-25mM/l. Ojil) /  produced  Figure  18.  activity  Electromyographic records  elicited  by e l e c t r i c a l  (EMGs) s h o w i n g  stimulation  locomotor  (A) o f t h e  pontobulbar locomotor s t r i p  (PLS) w h i c h was b l o c k e d b y GABA  infusion  ( B ) . A: A l t e r n a t i n g h i n d l i m b  i n t o t h e same s i t e  locomotion e l i c i t e d the  by e l e c t r i c a l  EMGs f r o m r i g h t  cranialis  muscles.  (RITC)  right  and l e f t  stimulation  and l e f t  B: The s t e p p i n g  b l o c k e d by i n j e c t i o n  stimulation (LITC)  as d e m o n s t r a t e d by  iliotibialis  locomotion e l i c i t e d  o f GABA i n t o t h e same s i t e .  ITC m u s c l e s  were t a k e n d u r i n g  (0-170uA) o f t h i s  PLS  148  site.  ramp  i n A was  The t r a c e s electrical  from  I  149  1  2s e c  i r r e v e r s i b l e b l o c k o f e l e c t r i c a l and p i c r o t o x i n (and b i c u c u l l i n e ) i n d u c e d locomotor b e h a v i o u r i n 2 a n i m a l s l a t e n c y t o muscimol-induced i n i t i a l injection t h e experiment  (N=2). The  b l o c k was 5-10 minutes a f t e r t h e  (0.2ul) and l a s t e d throughout  t h e course o f  (30 & 70 m i n u t e s ) . A d d i t i o n a l i n j e c t i o n s o f  p i c r o t o x i n and e l e c t r i c a l s t i m u l a t i o n were i n e f f e c t i v e a t e l i c i t i n g f u r t h e r l o c o m o t i o n from t h e muscimol i n j e c t i o n s i t e i n e i t h e r animal. In one a n i m a l injection  (N=l), b i c u c u l l i n e  (lOmM/ljil) i n t o PLS produced  (GABAA  antagonist)  locomotor a c t i v i t y  o f 15 minutes l a s t i n g f o r 30 minute e x p e r i m e n t a l p e r i o d ) appeared s i m i l a r t o t h a t seen f o l l o w i n g p i c r o t o x i n  (onset which  injection.  C e n t r a l Nucleus M e d u l l a , d o r s a l p a r t (Cnd)  Injection of picrotoxin i n e f f e c t i v e a t promoting  (5mM) i n t o Cnd (N=3) was  chemical-induced locomotion or reducing  e l e c t r i c a l s t i m u l a t i o n t h r e s h o l d . Muscimol (6.25mM) (N=l) i n j e c t i o n had no b l o c k i n g e f f e c t on e l e c t r i c a l s t i m u l a t i o n - i n d u c e d locomotor b e h a v i o u r i n one a n i m a l .  C e n t r a l Nucleus M e d u l l a , v e n t r a l p a r t (Cnv)  I n j e c t i o n s o f p i c r o t o x i n i n t o Cnv (5-20mM) i n 4 out o f 8 b i r d s e l i c i t e d l o n g l a s t i n g w a l k i n g (hopping i n 1 b i r d ) (see F i g u r e 19A,B) w i t h an onset o f f i r s t a c t i v i t y a p p e a r i n g a t a mean t i m e o f 13.5 minutes (range 4-22 m i n u t e s ) . I n one o f t h e remaining animals, p i c r o t o x i n  (25mM) decreased 150  electrical  Figure  19.  Electromyographic  GABA-reversible injection  locomotor a c t i v i t y  into the c e n t r a l nucleus  ( C n v ) . A: A l t e r n a t i n g (RITC).and l e f t picrotoxin elicited into  (LITC)  stepping  (EMGs)  elicited  showing by p i c r o t o x i n  of the medulla,  by p i c r o t o x i n  were t a k e n d u r i n g  ventral  a s r e p r e s e n t e d by EMGs f r o m  iliotibialis cranialis  muscles  i n j e c t i o n i n t o Cnv. B: The s t e p p i n g  t h e same s i t e .  (0-170LIA,  records  locomotion  f r o m r i g h t and l e f t  ramp e l e c t r i c a l  arrow under bottom t r a c e  151  stimulation indicates  right  following  i n j e c t i o n was b l o c k e d by i n f u s i o n  The t r a c e s  part  o f GABA  ITC m u s c l e s  o f t h i s Cnv 170jxA) .  site  152  threshold  f o r locomotion  picrotoxin  injection  from  100 t o lOpA,  (lOmM) r e s u l t e d  o f b o t h w i n g s and l e g s w i t h o u t  while i n y e t another,  i n long l a s t i n g  any r h y t h m i c p a t t e r n s o f  l o c o m o t i o n . A l l o f t h e above l o c o m o t i n g a n i m a l s degree  o f b o t h w i n g and l e g e x t e n s o r a c t i v i t y  period  o f locomotor  no  behaviour. Only  reaction to picrotoxin GABA  reversibly  (6.25mM)  both p i c r o t o x i n  birds  displayed  (<1 m i n u t e ) ,  = 9-14 m i n u t e s )  f o r p i c r o t o x i n and  ( F i g . 19B), w h i l e  blocked  and  (time t o o n s e t  muscimol  of the block  and e l e c t r i c a l s t i m u l a t i o n - i n d u c e d  i n one o f two b i r d s .  Pontine R e t i c u l a r  Picrotoxin  electrically  Formation  (5mM)  lasting  (RP)  stimulated locomotion  >35 m i n u t e s )  i n t o RP  onset  in  a n d 21 m i n u t e s  one b i r d  into  (3mM) f o r  (Figure 20).  (<1 m i n u t e ) .  t h e GABA i n j e c t i o n s  response  The b l o c k l a s t i n g  i n the other  i n both f o r 12  (Figure 20). S i m i l a r t o  Cnv, t h e b l o c k was t r a n s i t o r y  and t i m e  block  (for e l e c t r i c a l  stimulation)  after  completion  injection.  GABA  immediately  (0.5M) was e f f e c t i v e  153  animals minutes  d e p e n d e n t , w i t h t h e most e f f e c t i v e occurring  10  (100->50/iA) i n two o f f o u r  (0.5M) b l o c k e d t h e p i c r o t o x i n  with a fast  (latency t o onset  or reduced the t h r e s h o l d  stimulated locomotion  b i r d s when i n j e c t e d GABA  range  stimulated locomotion  (N=2) i r r e v e r s i b l y  locomotion  minutes:  one o f e i g h t  blocked or increased threshold  <9 m i n u t e s )  some  following the  i n t o Cnv (N=3) r a p i d l y  (mean = 11.5 m i n u t e s ;  electrically  displayed  injection.  (0.5M) i n f u s i o n  transiently  extension  at blocking  of the  electrically  F i g u r e 20.  E l e c t r o m y o g r a p h i c r e c o r d s (EMGs) showing  G A B A - r e v e r s i b l e locomotor a c t i v i t y e l i c t e d by e l e c t r i c a l s t i m u l a t i o n and p i c r o t o x i n i n f u s i o n i n t o t h e v e n t r a l p o n t i n e reticular  f o r m a t i o n (RP). STIM; EMGs from r i g h t  (LPECT) p e c t o r a l i s muscles and r i g h t i l i o t i b i a l i s cranialis  (RPECT) and l e f t  (RITC) and l e f t  (LITC)  muscles d u r i n g e l e c t r i c a l s t i m u l a t i o n o f  t h e s i t e shown ( f i l l e d t r i a n g l e ) i n t h e c o r o n a l s e c t i o n a t t h e bottom r i g h t . T h r e s h o l d e l e c t r i c a l s t i m u l a t i o n evoked a l t e r n a t i n g h i n d l i m b s t e p p i n g as shown by t h e a c t i v i t y o f t h e ITC muscles. PICRO ( T I P ) : Ten minutes (T10) a f t e r p i c r o t o x i n i n f u s i o n i n t o t h e same s i t e , locomotor a c t i v i t y appeared b o t h i n t h e wings (PECT) and l e g s (ITC). PICRO (T30): The l o c o m o t i o n c o n t i n u e d , as e v i d e n c e d by t h e EMGS showing a l t e r n a t i n g s t e p p i n g a c t i v i t y , a t T30. GABA: GABA i n j e c t i o n a t T35 b l o c k e d t h e p i c r o t o x i n - i n d u c e d l o c o m o t i o n t r a n s i e n t l y , as seen from t h e ITC EMG t r a c e s . PICRO: The p i c r o t o x i n - i n d u c e d l o c o m o t i o n r e t u r n e d , however, as seen by t h e h i n d l i m b EMG t r a c e s a t 55 minutes post-injection  (T55). A b b r e v i a t i o n s : BC - brachium  c o n j u n c t i v i u m , MLF - m e d i a l l o n g i d t u d i n a l f a s c i c u l u s , N V I abducens nerve, N V I I - v e s t i b u l a r nerve, R - raphe n u c l e u s , RP - n u c l e u s r e t i c u l a r i s p o n t i s , Rpc - p a r v o c e l l u l a r p a r t , p o n t i n e reticular  f o r m a t i o n , V I - abducens n u c l e u s , VS - t r i g e m i n a l  sensory n u c l e u s .  154  induced birds  locomotion  (stimulation  i n which p i c r o t o x i n  maximum 170/iA) i n two o t h e r  i n j e c t i o n was i n e f f e c t i v e a t e l i c i t i n g  locomotion. Muscimol quality  or the threshold  activity. was to  (6.25mM) i n j e c t e d  Picrotoxin  into  one s i t e  f o re l e c t r i c a l l y  injection  (5mM)  stimulated  following  i n e f f e c t i v e at changing the s t i m u l a t i o n evoke l o c o m o t i o n  from t h i s  Mesencephalic R e t i c u l a r  Bilateral  hindlimb  d i d n o t change t h e locomotor  muscimol  parameters  infusion necessary  site.  Formation  (MRF)  s t e p p i n g p r o d u c e d by e l e c t r i c a l  stimulation  o f t h e m e s e n c e p h a l i c r e t i c u l a r f o r m a t i o n was b l o c k e d  transiently  by GABA i n f u s i o n  8-12 m i n u t e s ) picrotoxin  i n two b i r d s .  (0.5M) i n f u s e d  <1 m i n u t e ;  I n one o f t h r e e a n i m a l s ,  lasting  infusion of  for electrically  f r o m 160 t o 90LIA o v e r a 70 m i n u t e p e r i o d . i n t o t h e same s i t e  (220/xA) . I n two o t h e r b i r d s , at e l i c i t i n g  long  l e g e x t e n s i o n w h i c h was a l s o Injection  (latency  (20mM) d e c r e a s e d t h e t h r e s h o l d  induced walking  effective  (0.5M)  of picrotoxin  increased  picrotoxin  the threshold  (5mM & lOmM) was  l a s t i n g f l y i n g behaviour with r e v e r s i b l e b y GABA  (3mM) i n t o  a more m e d i a l  156  tonic  infusion. injection  i n t h e MRF o f one a n i m a l h a d no e f f e c t on e l e c t r i c a l l y locomotion.  GABA  site  induced  DISCUSSION  P o n t o b u l b a r Locomotor S t r i p (PLS)  The i n j e c t i o n o f GABA a n t a g o n i s t s  p i c r o t o x i n and  b i c u c u l l i n e i n t o t h e PLS evoked l o c o m o t i o n which c o u l d be b l o c k e d by GABA o r muscimol.  These r e s u l t s a r e s i m i l a r t o t h o s e  found i n t h e c a t , where p i c r o t o x i n i n j e c t i o n e l i c i t e d muscimol/GABA-reversible  locomotion  f u r t h e r v e r i f y our c o n t e n t i o n and mammalian PLS. Noga e t al.  (Noga e t a l . , 1988) and  o f t h e homology between t h e a v i a n (1988) suggest t h a t t h e PLS i s  under GABAergic i n h i b i t o r y c o n t r o l and s t a t e as e v i d e n c e  that  l o c o m o t i o n c o u l d be e l i c i t e d by t r i g e m i n a l f i e l d s t i m u l a t i o n f o l l o w i n g PLS i n j e c t i o n o f p i c r o t o x i n , n e i t h e r o f which  alone  a c t i v a t e d t h e b e h a v i o u r . They argue from t h e s e r e s u l t s t h a t t h e PLS i s synonymous w i t h t h e d e s c e n d i n g t r a c t o f t h e t r i g e m i n a l nerve  (TTD) t h a t sends e f f e r e n t s v i a p r o p r i o s p i n a l pathways t o  more c a u d a l TTD and a l s o t o r e t i c u l a r f o r m a t i o n neurons.  They  a l s o argue t h a t s t i m u l a t i o n o f PLS (TTD) r e s u l t s i n l o c o m o t i o n t h r o u g h secondary a c t i v a t i o n o f t h e r e t i c u l a r neurons t h a t a d i r e c t r o l e i n the i n i t i a t i o n of locomotion 1988)  play  (Noga e t a l . ,  ( f o r d i s c u s s i o n o f e f f e r e n t TTD pathways see Chapter 3 ) . As seen i n t h e c a t , t r i g e m i n a l f i e l d s t i m u l a t i o n  or s t r o k i n g o f t h e head) o f t h e b i r d s h o r t l y  ( a i r puffs  following  p i c r o t o x i n i n f u s i o n b u t b e f o r e t h e onset o f l o c o m o t i o n e l i c i t e d by p i c r o t o x i n a l o n e appeared t o i n i t i a t e l o c o m o t i o n . Loud n o i s e a l s o e l i c i t e d bouts o f l o c o m o t i o n p r i o r t o t h e onset o f neurochemical i n d u c e d l o c o m o t i o n . I n a d d i t i o n , s t r o k i n g o f t h e  head r e g i o n f o l l o w i n g the appeared  t o augment t h e  behaviour.  I t appears  peripheral  stimulation,  overall  gain of the  locomotor  force  from  of p i c r o t o x i n - i n d u c e d locomotion  o f s t e p p i n g and/or  these  results,  a c t i n g through  system  behaviour  While  onset  and  f r o m PLS/TTD  no p r o j e c t i o n s  have b e e n e l u c i d a t e d  therefore, that  TTD,  facilitate  flapping  may  the  i n c r e a s e the  induction  stimulation.  o f GABAergic neurons t o the  in bird,  i n the r a t , Mugnaini  t e r m i n a l s i n TTD  McGeer  a f f e r e n t s t o TTD  McGeer, p e r s o n a l c o m m u n i c a t i o n ) . indicate that effects  TTD  observed  supposition The  GABAergic  remains  t o be  Although  bodies and  control  i n f o r m a t i o n by afferent  (1988) t h a t t h e  I hypothesize that trigeminal  TTD  to r e t i c u l a r  the  motor  this  of PLS-associated the  PLS/trigeminal/LRF reflex  initiation  GABAergic i n t e r n e u r o n s  and p o s s i b l y  down-regulating  i n p u t on  of  combined w i t h  "provides a substrate f o r sensorimotor  modulate a f f e r e n t  data  subserve  the v e r a c i t y  (E.  determined.  i s p r e s e n t l y unknown, b u t  locomotion",  internuclear  the present  i n t e r n e u r o n s may  GABA p l a y s i n t h e  h y p o t h e s i s o f Noga e t a l .  However,  have n o t b e e n r e p o r t e d  i n our experiments,  role that  locomotion  signals  cell  (1981) r e p o r t a v a r i e t y o f p r o p o s e d G A B A e r g i c p a t h w a y s ,  GABA-containing  of  Oertel  a l o n g i t s r o s t r o c a u d a l e x t e n t . McGeer  many o f w h i c h a r e i n t e r n e u r o n a l i n o r i g i n .  system  PLS/TTD  and  (1985) r e p o r t t h e p r e s e n c e o f b o t h G A B A - c o n t a i n i n g and  of  centrally  generated  o r dampening t h e e f f e c t s  b e f o r e TTD  sends  of  locomotion^producing  formation or other l o c o m o t o r - r e l a t e d  structures.  158  may  this  C e n t r a l Nucleus M e d u l l a ,  d o r s a l p a r t (Cnd)  I n j e c t i o n o f GABA a g o n i s t s and a n t a g o n i s t s were i n e f f e c t i v e at modulating  locomotor b e h a v i o u r  f o l l o w i n g i n j e c t i o n i n t o Cnd.  These r e s u l t s c o r r e l a t e w i t h t h o s e found by Noga e t al.  (1988)  f o r t h e c a t , where e l e c t r i c a l s t i m u l a t i o n e l i c i t e d , b u t picrotoxin injection failed to e l i c i t ,  locomotion.  They suggest  t h a t t h e e l e c t r i c a l s t i m u l a t i o n was a c t i v a t i n g f i b e r s from t h e PLS/TTD t o more m e d i a l b r a i n s t e m  reticular  travelling  formation  s t r u c t u r e s . Our r e s u l t s , however, demonstrate t h a t i n j e c t i o n o f c h o l i n e r g i c and e x c i t a t o r y amino a c i d a g o n i s t s i n t o Cnd e l i c i t s locomotion,  i n d i c a t i n g t h a t Cnd i n t r i n s i c neurons a r e capable o f  a c t i v a t i n g locomotion. A d i f f e r e n t explanation f o r the lack o f GABAergic e f f e c t s i n t h i s r e g i o n may l i e i n t h e d i f f e r e n t i a l d i s t r i b u t i o n o f GABAergic r e c e p t o r s and t e r m i n a l s i n t h e brainstem.  Although  l i t t l e i n f o r m a t i o n i s a v a i l a b l e f o r GABA  d i s t r i b u t i o n s i n b i r d s , i n t h e r a t , Mugnaini and O e r t e l  (1985)  show o n l y low l e v e l s o f GABA t e r m i n a l s i n t h e r e g i o n s m e d i a l t o TTD (Cnd i n b i r d ; FTL i n c a t ) , w h i l e h i g h e r l e v e l s were found i n TTD.  I t i s l i k e l y t h a t w i t h e l e c t r i c a l s t i m u l a t i o n o f Cnd, b o t h  f i b e r s o f passage from TTD and c e l l b o d i e s are b e i n g a c t i v a t e d , w h i l e c h e m i c a l  ( d e n d r i t e s ) i n Cnd  s t i m u l a t i o n a c t i v a t e s only  Cnd r e c e p t o r s . Thus, w h i l e a c e t y l c h o l i n e and t h e e x c i t a t o r y amino a c i d s appear t o be i n v o l v e d i n locomotor c o n t r o l v i a Cnd, GABA does n o t appear t o be a c t i v e as a n e u r o t r a n s m i t t e r region of the brainstem  i n this  i n e i t h e r t h e b i r d o r c a t (Noga e t a l , ,  1988).  159  Central  Nucleus Medulla,  v e n t r a l p a r t (Cnv)  GABAergic a n t a g o n i s t s  i n j e c t e d i n t o Cnv p r o d u c e d  or caused a decrease  in electrical  required  l o c o m o t i o n . B o t h e f f e c t s c o u l d be  by  to initiate  GABA o r m u s c i m o l  those  injection.  threshold blocked  These r e s u l t s a r e s i m i l a r t o  f o u n d i n t h e c a t (Noga e t a l . , 1988; G a r c i a - R i l l a n d  Skinner,  1987) f o l l o w i n g  Garcia-Rill stimulated medial  and S k i n n e r  reticular  greater  (1987) r e p o r t e d  formation,  infusion into the picrotoxin or at  immediately  locomotor behaviour  t o n i c extensor a c t i v i t y  our studies  (unpublished  i n birds using  observations),  somatotopic organization observations  following  have shown t h a t  hindlimb walking  o f b o t h wings and l e g s t o  b y Noga e t al. electrical  (1988),  i t i s possible that  small will  lateromedial often  These r e s u l t s are,  Taken t o g e t h e r  neurochejnical-induced  a locomotor Our  translocations  stepping to  however, s e l d o m s e e n f o r i n the vast  with the information  locomotion t r i a l s ,  160  formation.  change t h e p a t t e r n o f  w i n g l o c o m o t i o n , where f l a p p i n g i s b i l a t e r a l o f cases.  and s i m i l a r  stimulation  from c o n t r a l a t e r a l u n i l a t e r a l  stepping.  eventually  exists i n the r e t i c u l a r  of the stimulating electrode  majority  concentrations  i n f u s i o n . However, a l l a n i m a l s i n w h i c h p i c r o t o x i n  d e g r e e s . As d i s c u s s e d  bilateral  of e l e c t r i c a l l y  one a n i m a l o f s e v e n  type a c t i v i t y  was e f f e c t i v e a t p r o d u c i n g  varying  but found t h a t  In t h e b i r d , only  demonstrated convulsant  displayed  agonists/antagonists.  block  i n j e c t i o n produced convulsions  t h a n 5mM.  picrotoxin  i n j e c t i o n o f GABA  l o c o m o t i o n w i t h GABA o r m u s c i m o l  bicuculline  to  stimulation  locomotion  some f e l i n e  that i n  muscle  g r o u p s showed a l o s s appears t h a t injection  the convulsant  on c e n t r e s  Equivalent  or  cell  cell  action  e x t e n s o r and/or  result  of picrotoxin  flexor  muscles  found i n the 1985).  i n l o c o m o t o r b e h a v i o u r i n d u c e d by GABA i n the bird.  o f GABAergic  bodies i n t h i s  fibers  (Hall  et a l . ,  or i n t r i n s i c  are available.  that  i n the  3  innervation  region  explored  o f [ H]GABA o n l y w i t h r e s p e c t t o  striatotegmental projections  reticulospinal  To o u r knowledge,  a n d n e u r o c h e m i s t r y have been  suggest t h e p r o b a b i l i t y  Cnv c e l l s  1984) a n d  GABA-containing  However, o u r r e s u l t s  giving  rise to  (Webster a n d S t e e v e s , 1988) a r e u n d e r  GABAergic  inhibitory  intrinsic  or e x t r i n s i c  birds  1985) may  s t r u c t u r e s may s e r v e a s t h e n e u r o a n a t o m i c a l s u b s t r a t e  using retrograde transport  reports  after  (Mugnaini and O e r t e l ,  i t s a g o n i s t s and a n t a g o n i s t s  GABAergic  (Franz,  1988), i t  out o f phase.  formation  t h e o b s e r v e d changes  bird  demonstrated  b o d i e s a n d t e r m i n a l s have b e e n  reticular  GABA neuroanatomy  no  different  a r e normally modulated  ventral  for  activity  e t al.,  (Noga  and subsequent d i s i n h i b i t o r y  controlling  GABAergic rat  activity  of the long acting p i c r o t o x i n  from d i f f u s i o n  which  of phasic  control. neurons  Whether t h i s  control  arises  from  r e m a i n s t o be d e t e r m i n e d b o t h f o r  a n d mammals.  Pontine R e t i c u l a r  F o r m a t i o n (RP)  Chemical s t i m u l a t i o n  o f t h e v e n t r a l RP r e g i o n w i t h t h e GABA  a n t a g o n i s t p i c r o t o x i n p r o d u c e d l o c o m o t i o n w h i c h was b l o c k e d by GABA i n f u s i o n .  W h i l e no d a t a i s a v a i l a b l e  bodies or terminals  i n the bird,  f o r GABAergic  cell  i n t h e r a t , medium t o low  161  l e v e l s o f GABA t e r m i n a l s and low t o v e r y low l e v e l s o f GABAergic c e l l b o d i e s have been found i n t h e p o n t i n e r e t i c u l a r f o r m a t i o n (Mugnaini and O e r t e l , 1985) . I t appears u n l i k e l y , t h a t GABAergic neurons  therefore,  i n t r i n s i c t o the pontine r e t i c u l a r  f o r m a t i o n a r e r e s p o n s i b l e f o r t h i s response. However, c e l l b o d i e s i n t h e p o n t i n e r e t i c u l a r f o r m a t i o n appear t o be under GABAergic  i n h i b i t o r y c o n t r o l . The g r e a t e r c o n c e n t r a t i o n o f  GABAergic t e r m i n a l s r e l a t i v e t o c e l l b o d i e s suggests an e x t r i n s i c source o f i n p u t . N e u r a l pathways which u n d e r l i e t h i s c o n t r o l a r e , however, p r e s e n t l y unknown, l e a v i n g any s i g n i f i c a n t locomotor r o l e f o r GABA i n t h e p o n t i n e r e t i c u l a r f o r m a t i o n undetermined.  M e s e n c e p h a l i c R e t i c u l a r F o r m a t i o n (MRF)  I n f u s i o n o f GABAergic  a n t a g o n i s t s and a g o n i s t s i n t o t h e MRF  was e f f e c t i v e i n e l i c i t i n g o r b l o c k i n g l o c o m o t i o n i n b i r d s . These r e s u l t s a r e s i m i l a r t o t h o s e found f o l l o w i n g t h e i n f u s i o n of GABAergic neurochemicals i n t o t h e MLR b o t h i n t h e d e c e r e b r a t e cat  ( G a r c i a - R i l l e t a l . , 1985) and t h e f r e e l y moving r a t  ( B r u d z y n s k i and Mogenson, 1986) . GABA i s p r e s e n t i n t h e cuneiform nucleus rat,  (CN) and p e d u n c u l o p o n t i n e n u c l e u s  (PPN) o f t h e  w i t h h i g h e r l e v e l s o f b o t h GABA-containing c e l l b o d i e s and  t e r m i n a l s b e i n g found i n t h e c u n e i f o r m n u c l e u s (Mugnaini and O e r t e l , 1985). P o s s i b l e l o c o m o t i o n - r e l a t e d GABAergic  projections  from t h e s u b s t a n t i a n i g r a , p a r s r e t i c u l a t a , n u c l e u s accumbens and e n t o p e d u n c u l a r n u c l e u s t o t h e PPN/MLR have been r e p o r t e d i n t h e c a t ( G a r c i a - R i l l e t al.,  1983b, G a r c i a - R i l l and S k i n n e r , 162  1986)  e t al.,  and r a t ( G a r c i a - R i l l  supported,  i n part,  1986).  by t h e d e s c r i p t i o n  These r e s u l t s  o f nucleus  were  accumbens  G A B A e r g i c p r o j e c t i o n s t o b o t h PPN a n d CN i n t h e r a t (Mogenson e t al.,  1985;  discussed  Mogenson a n d Wu,  1986;  and m e d i a l  mesencephalic  e t a l . , 1985;  (Garcia-Rill 1988),  1988).  As  i n t h e p r e v i o u s c h a p t e r , t h e mammalian CN a n d PPN,  w h i c h may r e p r e s e n t t h e n e u r o a n a t o m i c a l lateral  e t al.,  Brudzynski  substrates f o r the  locomotor  Noga e t al.,  1988;  a p p e a r t o be e q u i v a l e n t t o t h e a v i a n  regions  s t i m u l a t e d i n our study. While  studies  localizing  been c a r r i e d  GABA-containing  out f o r these  regions  Brudzynski  t o o u r knowledge, no  cell  found  evidence which supports t h e presence  al.,  et  mesencephalic  bodies  o r t e r m i n a l s have  regions i n the bird,  t h e mammalian r e s u l t s w i t h t h o s e  respectively,  comparison  above i n b i r d s  of  provides  o f an a v i a n e q u i v a l e n t o f  t h e mammalian MLR. However", due t o t h e s m a l l number o f mesencephalic locomotion  injection  sites  following a single  more m e d i a l  MRF,  and t h e i n a b i l i t y injection  further testing  of this  to elicit  of picrotoxin hypothesis  into the  i s required  b e f o r e any f i r m e q u i v a l e n c y c a n be e s t a b l i s h e d .  Pharmacological Considerations  Picrotoxin identified  locomotor  transiently appeared  into  a variety  regions also  subthreshold  of picrotoxin  of e l e c t r i c a l l y  elicited  r e v e r s e d w i t h GABA i n f u s i o n ,  t o be i r r e v e r s i b l y  Furthermore, injection  injection  l o c o m o t i o n w h i c h was  a n d i n some c a s e s ,  b l o c k e d by m u s c i m o l  (for e l e c t r i c a l l y  decreased  163  injection.  evoked  the e l e c t r i c a l  locomotion)  stimulation  i n t e n s i t y necessary  t o evoke  locomotion.  P h a r m a c o l o g i c a l l y , t h e s e r e s u l t s appear somewhat p e r p l e x i n g , as p i c r o t o x i n has been demonstrated t o a c t a t d i f f e r e n t r e c e p t o r s i t e s t h a n GABA, muscimol and b i c u c u l l i n e (Olsen, 1981). How t h e n does GABA o r muscimol r e v e r s e t h e locomotor a c t i o n o f p i c r o t o x i n ? P i c r o t o x i n i s a potent a n t a g o n i s t a t b o t h t h e GABA  ft  (Krogsgaard-Larsen  et a l . ,  and G A B A  b  r e c e p t o r subtypes  1983). The GABA  ft  receptor  ( d e f i n e d by  i t s s e n s i t i v i t y t o the competetitive antagonist b i c u c u l l i n e ) , i s thought t o c o n t r o l a c h l o r i d e ionophore (Krogsgaard-Larsen al.,  1983) and has been demonstrated t o p o s s e s s f i v e  et  different  b i n d i n g s i t e s i n c l u d i n g a GABA a g o n i s t / a n t a g o n i s t ( i n c l u d i n g muscimol and b i c u c u l l i n e ) s i t e , a b e n z o d i a z e p i n e p i c r o t o x i n s i t e , a depressant  site  site, a  (e.g. b a r b i t u r a t e s ) and a  s i t e ( s ) which b i n d s t h e c h a n n e l - p e r m e a t i n g i o n s 1987) . The GABA  receptor  (Barnard e t a l . ,  ( d e f i n e d by i t s s e n s i t i v i t y t o t h e  B  a g o n i s t b a c l o f e n ) , on t h e o t h e r hand, i s b e l i e v e d t o e x e r t i t s e f f e c t s by r e s t r i c t i n g p r e s y n a p t i c influx  ( v o l t a g e dependent) c a l c i u m  (Desarmenien e t a l . , 1983).  As d i s c u s s e d i n Chapter 3, t h e e l i c i t a t i o n o f l o c o m o t i o n by neurochemical i n j e c t i o n i s viewed as a r e c r u i t m e n t phenomenon whereby a s u f f i c i e n t number o f neurons must be a c t i v a t e d o r b l o c k e d by t h e neurochemical t o i n i t i a t e / b l o c k t h e v i s i b l e of l o c o m o t i o n  signs  (see Chapter 3 ) . I n t h i s study, i t i s n o t p o s s i b l e  t o determine whether t h e i n h i b i t o r y a c t i o n o f p i c r o t o x i n on GABA r e c e p t o r s i s a c t i n g p r e - s y n a p t i c a l l y , p o s t s y n a p t i c a l l y o r both, although the e f f e c t i v e n e s s of b i c u c u l l i n e at e l i c i t i n g locomotion  would suggest t h a t GABA  ft  164  and n o t G A B A  b  receptors  mediate t h e e f f e c t . should  Introduction  not occupied  picrotoxin  by p i c r o t o x i n , t h e r e b y  (Franz,  induced  agonist  locomotion.  (Bloom,  suggestion agonist  that  following  locomotion  o f p i c r o t o x i n . The  a potent,  long  lasting  GABA^  locomotion  t h e same mechanism a n d u n d e r l i e s t h e  GABA  receptors  ft  and a n t a g o n i s t  electrical  to reverse the  f o rthe return of  1 9 8 5 ) on p i c r o t o x i n - i n d u c e d  presumably u t i l i z e s  T h i s may a l s o  The r a p i d breakdown o f GABA i n  1 9 8 5 ) would account  a c t i o n o f muscimol,  may be t h e t a r g e t o f t h e GABA  locomotor e f f e c t s .  stimulation intensity subthreshold  necessary  Furthermore, the t o evoke  locomotion  ( f o r l o c o m o t i o n ) p i c r o t o x i n i n f u s i o n may  augment t h e number o f n e u r o n s a c t i v a t e d by p i c r o t o x i n , eliciting In  at reduced e l e c t r i c a l  future studies, d i f f e r e n t i a t i o n  receptor  and  locomotion  subtype u n d e r l y i n g  phaclofen  (Karlsson et  further valuable control  of  al.,  information  1988).  locomotion.  165  GABA  GABA  a + b  the role  agonists  antagonist  Such s t u d i e s w o u l d  concerning  GABA  observed i n t h i s  more s p e c i f i c  s u c h as t h e n e w l y r e p o r t e d  thereby  threshold.  of the avian  the locomotion  may be p o s s i b l e u t i l i z i n g  antagonists  which  c i r c u i t i n g the  o f GABA n e c e s s a r y  b y t h e more p e r s i s t e n t b i n d i n g  inhibitory  short  and b l o c k i n g l o c o m o t i o n .  concentration  picrotoxin-induced  study  o f GABA  e f f e c t s by b i n d i n g t o GABA r e c e p t o r s  inhibition  explain the high  vivo  concentration  n o t d i s p l a c e t h e bound p i c r o t o x i n , b u t may e x e r t i t s  locomotor i n h i b i t o r y are  of a high  provide  o f GABA  i n the  CHAPTER 5 CHARACTERIZATION OF AVIAN MID- AND HINDBRAIN SITES THAT PRODUCE LOCOMOTION WITH INTRACEREBRAL INFUSION OF NEUROTRANSMITTER AGONISTS AND ANTAGONISTS ( I I I ) : EXCITATORY AMINO ACIDS AND SUBSTANCE P  166  INTRODUCTION  Previous chapters  (3 & 4) i n t h i s t h e s i s have demonstrated  that s i t e s p e c i f i c i n t r a c e r e b r a l microinjection of c h o l i n e r g i c and GABAergic n e u r o t r a n s m i t t e r  a g o n i s t s and a n t a g o n i s t s are  e f f e c t i v e at e l i c i t i n g or b l o c k i n g locomotor behaviours i n decerebrate  b i r d s . Furthermore, attempts were made t o d e s c r i b e a  p o s s i b l e neuroanatomical chapter  s u b s t r a t e f o r those e f f e c t s . T h i s  surveys the e f f e c t s o f i n j e c t i o n o f glutamate, i t s  a g o n i s t s or a n t a g o n i s t s i n t o s e v e r a l locomotor r e g i o n s p r e v i o u s l y i d e n t i f i e d by e l e c t r i c a l s t i m u l a t i o n (Steeves 1986, 1987; Sholomenko and Steeves,  et  al.,  1987a,b, 1988). R e s u l t s o f  Substance P i n f u s i o n i n t o s e v e r a l s i t e s w i l l a l s o be d e s c r i b e d . The r e s u l t s demonstrate t h a t m i c r o i n j e c t i o n o f the glutamate a g o n i s t NMDA i n t o v a r i o u s locomotor r e g i o n s was e f f e c t i v e at evoking elicited  locomotion  locomotor behaviour  i n b i r d s . Substance P  i n only one r e g i o n i n j e c t e d . These r e s u l t s  w i l l be c o r r e l a t e d with i n t e r s p e c i f i c  neuroanatomical,  immunohistochemical and r e c e p t o r a u t o r a d i o g r a p h i c data i n an attempt t o e l u c i d a t e and compare the n e u r a l s u b s t r a t e c o n t r o l l i n g locomotion  across a broad  species.  167  range o f v e r t e b r a t e  MATERIALS AND METHODS  The m a t e r i a l s procedure, injection  a n d methods,  including the decerebration  e l e c t r i c a l s t i m u l a t i o n methodology, parameters and h i s t o l o g i c a l  stimulation/injection  sites  neurochemical  identification of  have b e e n p r e v i o u s l y d e s c r i b e d i n  C h a p t e r s 2 & 3.  168  RESULTS  E x c i t a t o r y Amino A c i d s A g o n i s t s , A n t a g o n i s t s a n d S u b s t a n c e P  Excitatory agonists, in  amino a c i d  (EAA) n e u r o t r a n s m i t t e r s , t h e i r  a n t a g o n i s t s and Substance  P were i n f u s e d  t h e h i n d - and m i d b r a i n t o determine t h e i r  evoking or i n h i b i t i n g  locomotion at s i t e s  c a n be e l i c i t e d b y f o c a l 1986).  NMDA, t h e g l u t a m a t e  receptor  subtype,  glutamatergic relatively  (Noga e t a l . ,  1988).  1988;  Substance  on l o c o m o t o r b e h a v i o u r . The s i t e s  distributed within  identified  (GDEE) , a  fasciculus.  concentration  T a b l e 3 and d e s c r i b e d sites  injected  were  dorsal  which  and v e n t r a l  formation, pontine  mesencephalic r e t i c u l a r  into  t o determine i t s  r e g i o n s o f t h e mid- and h i n d b r a i n  o f the medullary r e t i c u l a r  longitudinal  injected  locomotor s i t e s  i n c l u d e d the pontobulbar locomotor s t r i p ,  injection  ester  putative  L a i a n d S i e g e l , 1988;  P was a l s o  effects  in  a t t h e NMDA  n o n - s p e c i f i c EAA a n t a g o n i s t was u s e d i n an a t t e m p t t o  electrically  effective  (Steeves e t a l , ,  a g o n i s t most e f f e c t i v e  receptors. Glutamic a c i d d i e t h y l  and Burton,  formation,  from which l o c o m o t i o n  stimulation  several  parts  effectiveness at  a n d g l u t a m a t e were i n f u s e d t o e x c i t e  b l o c k EAA r e c e p t o r s Stone  electrical  into regions  reticular  f o r m a t i o n and m e d i a l  Neurochemical  injection  sites,  and time c o u r s e o f a c t i v i t y i n t h e t e x t . A composite  i s shown i n F i g u r e 2 1 .  169  lowest  are l i s t e d  diagram o f  TABLE 3 Excitatory Amino Acids and Substance P Animal  Site  Chemical  TTD  Glutamate NMDA GDEE Substance P  Cnd  Cnv  pH  "  NMDA GDEE Substance P  »  Glutamate NMDA GDEE Substance P  ••  ••  " '•  " "  Concentrations Injected  Lowed Volume Effective Concentration  0.SO.0M eOmM 2-B0mM S.44mM  none 80mM 2mM none  1.0ul 0.2ul 0.4-1 ul 1.0ul  — <1  20-83mM 80mM 6.44mM  20mM 80mM none  0.2ul o.eui 1.0ul  <1.5 <5  3-24 >35  1M 4-83mM 2-B0mM 6.44mM  none 4mM 2mM none  I.Oul 0.4 ul 0.2ul 1.0ul  — — <1  — — 3-4  4-6  35-50  Time Courts (min) Latency Period  B1-83mM 6.44 mM  83mM 6.44 mM  0.2ul 1.0ul  4-6  —  —  <1-1.25 4  —10 35-55  —  —  4-8 >15  RP  NMDA 7.2-7.4 Substance P "  MRF  NMDA  "  6-34mM  5mM (RT)  0.2ul  5  15  MLF  NMDA  ••  20-34mM  34mM  0.4ul  <1  8  ABBREVIATIONS: Cnd Cnv MLF MRF RP RT TTD  Rate  — — — — — — —  dorsal part, medullary central nucleus ventral part, medullary central nucleus medial longitudinal fasciculus mesencephalic reticular formation pontine reticular nucleus reduced threshold lor electrically stimulated locomotion descending trigeminal tract and nucleus  170  Figure  21.  Composite diagram o f g l u t a m a t e r g i c a g o n i s t and  neurochemical  antagonist  sections through in  upper l e f t  mm)]  t h e locomotor  r e g i o n s from  electrical (filled  various levels  sites.  A=anterior,  effects  which locomotion  s t i m u l a t i o n . Where g l u t a m i c  square)  The d i a g r a m o f c o r o n a l  of the avian neuraxis  corner o f each l e v e l ,  illustrates  brainstem  injection  i s shown a s f i l l e d ,  o f each  P=posterior ( i n  neurochemical  was f i r s t  in  e l i c i t e d by  acid diethyl  i t s effect  [numbers  ester  (GDEE)  was t o b l o c k  locomotion.  Key  A b b r e v i a t i o n s : GDEE - g l u t a m i c  glutamate, -  acid  NMDA - N - m e t h y l - D - a s p a r t a t e ,  locomotion  (except  f o r GDEE),  diethyl  ester,  GLUT -  SUBP - s u b s t a n c e  TH - d e c r e a s e d  P; LOCO  electrical  threshold  intensity  f o r locomotion,  ^TH - i n c r e a s e d  threshold  intensity  f o rlocomotion,  NR - no  electrical  response.  F i g u r e A b b r e v i a t i o n s : AL - a n s a l e n t i c u l a r i s , AQ - a q u e d u c t , BC - b r a c h i u m c o n j u n c t i v u m , CC - c e n t r a l c a n a l , Cnd - c e n t r a l n u c l e u s m e d u l l a , d o r s a l p a r t , Cnv - c e n t r a l n u c l e u s m e d u l l a , v e n t r a l p a r t , EM - e c t o m a m m i l l a r y n u c l e u s , EW - E d i n g e r W e s t p h a l n u c l e u s , I I I - o c c u l o m o t o r n u c l e u s , 10 - i n f e r i o r o l i v a r y n u c l e u s , IP - n u c l e u s i n t e r p e d u n c u l a r i s , LC - l o c u s c o e r u l e u s , MLd - l a t e r a l m e s e n c e p h a l i c n u c l e u s , d o r s a l d i v i s i o n , MLF m e d i a l l o n g i t u d i n a l f a s c i c u l u s , MRF - m e d i a l mesencephalic r e t i c u l a r f o r m a t i o n , MV - t r i g e m i n a l motor n u c l e u s , N I I I occulomotor nerve, N IV - t r o c h l e a r nerve, N X I I - h y p o g l o s s a l n e r v e , OT - o p t i c t e c t u m , R - r a p h e n u c l e u s , RP - n u c l e u s p o n t i n e r e t i c u l a r f o r m a t i o n , Rpc - p o n t i n e p a r v o c e l l u l a r r e t i c u l a r n u c l e u s , RPO - n u c l e u s r e t i c u l a r i s p o n t i s o r a l i s , Ru r e d n u c l e u s , SSP - s u p r a s p i n a l n u c l e u s , SV - t r i g e m i n a l s e n s o r y n u c l e u s , T P c - s u b s t a n t i a n i g r a , TTD - t r i g e m i n a l d e s c e n d i n g t r a c t and n u c l e u s , X - d o r s a l motor n u c l e u s vagus.  171  A 3.75 LOCO JTH TTH  ffi  NBA  •  ©  e  O  GDS  D  B  B  •  GLUT  •  •  •  O  SUBP A  A A A  172  Pontobulbar  L o c o m o t o r S t r i p (PLS)  F o l l o w i n g e s t a b l i s h m e n t o f a low i n t e n s i t y point  f o r evoking locomotion,  (N=3) e l i c i t e d injected a rapid for  injection  repeatable bouts  (<lmin)  approximately  stimulated  o f NMDA  (80mM/0.2ul)  o f locomotion i n 2 o f 3 b i r d s  ( F i g . 2 2 ) . The l o c o m o t i o n onset  stimulation  f o l l o w e d NMDA i n j e c t i o n  and o c c u r r e d i n v i g o r o u s bouts  10 m i n u t e s .  with  (l-2min)  B o t h NMDA a n d e l e c t r i c a l l y  l o c o m o t i o n were i r r e v e r s i b l y  b l o c k e d b y GDEE  (80mM/0.4ul a n d 2mM/0.2ul) f o r t h e d u r a t i o n o f t h e e x p e r i m e n t (>40min)  (Figure 22C). Glutamate  i n t o PLS h a d no e f f e c t stimulated  locomotor  a l s o h a d no e f f e c t  C e n t r a l Nucleus,  Injection elicited  Substance  P (N=l) (5.44mM/l.Oul)  when i n f u s e d  into this  site.  injection,  and l a s t e d  behaviour  f o r 3 a n d 14 m i n u t e s .  electrical  only b i l a t e r a l  stimulation  (<1 min) a n d l o n g l a s t i n g  produced  onset (  Prior to  i n one o f t h e s e  s t e p p i n g movements,  ( F i g . 2 6 A ) . One o f f i v e  f o l l o w i n g NMDA s t i m u l a t i o n that  i n 2/5 b i r d s  ( F i g . 2 3 B ) . The l o c o m o t i o n o c c u r r e d w i t h f a s t  b o t h r u n n i n g a n d f l y i n g were d i s p l a y e d  threshold onset  behaviour.  o f NMDA i n t o Cnd (81-83mM/0.2ul)  animals produced other,  of electrically  d o r s a l p a r t (Cnd)  & 1.5 m i n u t e s )  chemical  on t h e t h r e s h o l d  (0.5-1.0M/1.Oul) (N=2)  r e p e a t a b l e b u r s t s o f r u n n i n g and f l y i n g  (20-40sec) 1.0  infusion  at e l e c t r i c a l  of thebirds  (24 m i n u t e s )  while i n the  displayed  walking  rapid  behaviour  (20mM/0.2ul) w h i c h was s i m i l a r t o  by p r e - i n j e c t i o n  electrical  stimulation.  In t h e  F i g u r e 22. activity into the  Electromyographic  records  e l i c i t e d by e l e c t r i c a l  a site  i n t h epontobulbar  coronal section  Alternating  (EMGs) s h o w i n g  locomotor  s t i m u l a t i o n a n d NMDA  injection  locomotor  o f the medulla  (bottom  (PLS)  right).  shown i n  STIM:  s t e p p i n g r e p r e s e n t e d b y EMG p a t t e r n s from  (RITC) a n d l e f t  (LITC)  i l i o t i b i a l i s cranialis  f l e x o r muscle) e l i c i t e d by e l e c t r i c a l activity  strip  i s present  i nthe right  muscles  stepping  (RPECT) a n d l e f t  wings 1st  (PECT) a n d l e g s  right  (ITC)  ITC muscles.  f o l l o w i n g GDEE i n f u s i o n i n t o NMDA a n d e l e c t r i c a l Abbreviations: nucleus, part,  trigeminal  N X -  muscles.  evoked b u r s t s o f  (only  s t i m u l a t i o n a t 20 m i n u t e s  s t e p p i n g a s shown b y t h e EMGs  GDEE: H i n d l i m b  t h e same s i t e  EMG r e c o r d s  which b l o c k e d  c a n a l , Cnd - c e n t r a l  d o r s a l p a r t , Cnv - c e n t r a l m e d u l l a r y  fasciculus,  No  further  stimulation-induced locomotion.  CC - c e n t r a l  10 - i n f e r i o r  hip  (LPECT)  a t 90 s e c o n d s p o s t - i n j e c t i o n  e l i c i t e d hindlimb  and l e f t  (major  a s shown b y t h e EMGs f o r t h e p a i r e d  b u r s t i s shown). STIM: E l e c t r i c a l  post-injection of  i n t o t h e same s i t e  and wing f l a p p i n g  right  s t i m u l a t i o n o f t h e PLS.  p e c t o r a l i s muscles which a r e t h e major wing d e p r e s s o r NMDA: NMDA i n j e c t i o n  the  olivary  nucleus,  vagus nerve,  descending  tract  medullary  nucleus,  MLF - m e d i a l  ventral  longitudinal  ST - s u b t r i g e m i n a l n u c l e u s ,  and n u c l e u s ,  nucleus.  174  X - vagal  motor  TTD -  Figure  23.  activity into  Electromyographic  elicited  the dorsal  Alternating patterns  alternating  stimulation  of the central  by e l e c t r i c a l  (in-phase)  (Cnd) A:  iliotibialis  stimulation  (LPECT)  pectoralis  o f Cnd. B:  EMGs  (PECT) a n d  EMGs e v o k e d b y i n j e c t i o n o f NMDA  i n t o t h e same s i t e .  C: EMG t r a c e s  i n j e c t i o n o f GDEE  (80mM/0.6ul)  during e l e c t r i c a l  stimulation  minutes a f t e r t h e i n f u s i o n  nucleus  r e p r e s e n t e d b y EMG  (LITC)  wing f l a p p i n g  locomotor  a n d NMDA i n j e c t i o n  medullary  (RITC) a n d l e f t  stepping.(ITC)  (83mM/0.2ul)  were t a k e n  (EMGs) s h o w i n g  m u s c l e s a n d r i g h t . (RPECT) a n d l e f t  Simultaneous  after  part  right  muscles e l i c i t e d  legs  by e l e c t r i c a l  s t e p p i n g and wing f l a p p i n g  from  cranialis  records  o f NMDA  into  from w i n g s a n d the site.  (170uA) o f t h e s i t e 4  (83mM/0.2ul) .  176  Traces  I  177  ! 1 sec  1  RITC  -ifr  *—  fKdfeif  4h"" t*' ")!** 1  LITC 0 . 5 sec  178  RPECT  LPECT  RITC  LITC 1  i  2 sec  179  bird  which d i s p l a y e d  electrical this  site  running/flying  a n d NMDA s t i m u l a t i o n , irreversibly  stimulated paralyzed  locomotion following  20mM/0.2Lil  aliquots  (hopping)  post-injection  Chapter  infusion  into  a n d NMDA  site  (see Chapter  o f NMDA r e p e a t a b l y in-phase  x  6), i n j e c t i o n o f  initiated  fictive'  b o u t s (-1.5  l e g movements  1 m i n u t e p o s t - i n j e c t i o n . The  electroneurographic  observed  blocked further e l e c t r i c a l  of bilateral  within  (80mM/0. 6jil)  e s t a b l i s h m e n t o f an a l t e r n a t i n g w a l k i n g  stimulation  long)  GDEE  with  ( F i g . 2 3 C ) . I n one b i r d w h i c h was  electrical  minutes  behaviour both  activity  appeared  strongest  immediately  a n d became weaker o v e r t i m e . No b o u t s  a f t e r approximately  6 minutes  were  p o s t - i n j e c t i o n (see  6, F i g . 33) .  Substance electrical  P (5.44mM)  stimulation  i n j e c t i o n produced  threshold  no c h a n g e s i n  when i n j e c t e d i n t o C n d i n one  animal.  Central  Nucleus,  v e n t r a l p a r t (Cnv)  NMDA i n j e c t i o n i n t o Cnv p r o d u c e d birds.  Electrical  stimulation, intensity  stimulation,  produced  ( F i g . 24A). Chemical  bouts  (latency animal in  (5-15 s e c o n d s )  t o onset  behaviour  at threshold  stimulation o f these animals  o f r u n n i n g and f l y i n g  resulted i n locomotion  <1 min) w h i c h c o n t i n u e d f o r 3 m i n u t e s  and 4 minutes  response  i nboth  i n 3 of3  c a r r i e d out p r i o r t o chemical  running and f l y i n g  (81mM/0.2Lil;4mM/0.4/il) short  locomotion  i n one  i n t h e o t h e r a n d was s i m i l a r t o t h a t  to electrical  stimulation  180  seen  ( F i g . 2 4 B ) . GDEE a t b o t h  F i g u r e 24. E l e c t r o m y o g r a p h i c r e c o r d s (EMGs) showing locomotor a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n  and NMDA i n j e c t i o n  i n t o t h e v e n t r a l p a r t o f t h e c e n t r a l m e d u l l a r y n u c l e u s (Cnv) A: A l t e r n a t i n g  s t e p p i n g and wing f l a p p i n g r e p r e s e n t e d by EMG  p a t t e r n s from r i g h t  (RITC) and l e f t  c r a n i a l i s muscles and r i g h t  (LITC)  iliotibialis  (RPECT) and l e f t  muscles e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n  (LPECT) p e c t o r a l i s  o f Cnv. B:  Simultaneous (in-phase) wing f l a p p i n g EMGs (PECT) and a l t e r n a t i n g stepping  (ITC) EMGs evoked by i n j e c t i o n o f NMDA  (4mM/0.4ul) i n t o t h e same s i t e . C: EMG t r a c e s  from wings and  l e g s a f t e r i n j e c t i o n o f GDEE (2mM/0.2fil) i n t o t h e s i t e . Traces were t a k e n 4 minutes a f t e r t h e i n f u s i o n o f NMDA  181  (4mM/0.4ul).  LITC i  182  0.5 sec  LITC  M  #' •  # 1  I  1  183  sec  c RPECT  LPECT  RITC  LITC  — 2 sec  184  high  (80mM/0.4ul) and low (2mM/0.2ul) c o n c e n t r a t i o n s  i r r e v e r s i b l y b l o c k e d both NMDA and e l e c t r i c a l l y locomotion when i n f u s e d i n t o these s i t e s  induced  ( F i g 24C). In the t h i r d  animal, e l e c t r i c a l s t i m u l a t i o n produced continuous b i l a t e r a l walking behaviour which was r e p e a t a b l y (5 t r i a l s ) mimicked by NMDA (83mM/0.2/il) i n j e c t i o n with short l a t e n c y time course  (<1 minute) and  (~4 min). Substance P (5.44mM/l. 0(il) i n j e c t i o n a t  t h i s s i t e had no e f f e c t e i t h e r on the q u a l i t y o f c h e m i c a l l y induced locomotion o r e l e c t r i c a l s t i m u l a t i o n  threshold.  In two other animals which r e c e i v e d Substance P (5.44mM/l. Ojil) i n j e c t i o n s i n t o Cnv,  no changes were observed i n  the locomotor p a t t e r n o r e l e c t r i c a l t h r e s h o l d needed t o i n i t i a t e locomotion. One o f the above b i r d s r e c e i v e d an i n j e c t i o n o f glutamate  (lM/l/il) i n t o the same s i t e 20 minutes  P i n j e c t i o n . Although the glutamate  after  Substance  i n j e c t i o n d i d not induce  locomotion or a f f e c t any changes t o s t i m u l a t i o n i n t e n s i t y threshold,  increases  i n b r e a t h i n g frequency and f o r c e o f  e x p i r a t i o n were observed which were s i m i l a r t o those seen r e s u l t i n g from e l e c t r i c a l s t i m u l a t i o n i n t h i s  site.  Pontine R e t i c u l a r Formation (RP)  Introduction  o f NMDA i n t o s i t e s i n the p o n t i n e r e t i c u l a r  formation e l i c i t e d locomotion i n 3 o f 5 b i r d s . One o f these animals d i s p l a y e d r u n n i n g / f l y i n g both at e l e c t r i c a l  stimulation  t h r e s h o l d and f o l l o w i n g NMDA (81mM/0. 4fil) i n f u s i o n . The l a t e n c y to onset o f r u n n i n g / f l y i n g was 1.25 minutes with short (15-25 seconds)  bouts  o f t h i s behaviour o c c u r r i n g f o r up t o 4.25 185  minutes  post-injection.  injections  The two o t h e r b i r d s w i t h RP NMDA  ( 8 3 m M / 0 . 2fil)  elicited  walking only  pre-injection  electrically  above a n i m a l s  r e p e a t a b l y produced  minute p o s t - i n j e c t i o n second  animal  Substance  (83mM/0.2/il)  4 minutes  w a l k i n g movements w i t h i n 1 approximately  r e c e i v e d NMDA 15 m i n u t e s  injection  weak b i l a t e r a l behaviour)  s t i m u l a t e d l o c o m o t i o n ) . One o f t h e  which l a s t e d  (5.44mM/lLil)  P  significantly stepping  ( F i g . 25C) p r o d u c e d post-injection  NMDA was i n j e c t e d ) approximately  after  into the site  alternating  4 m i n u t e s . The  injection of  ( F i g . 25A,B) . The NMDA  increased the force (and i n i t i a t e d  by a Substance  lasting  within  (similar t o  The e f f e c t  9 minutes  and decreased  Reticular  F o r m a t i o n (MRF)  flapping  P injection  up t o 15 m i n u t e s  1 minute.  of the  a t which  o f NMDA  i n a time  (onset time  lasted  dependent  manner.  Mesencephalic  NMDA i n j e c t i o n reduced  (5mM/0.2/jl)  the threshold  i n t o t h e MRF i n one o f two b i r d s  for electrically  t o 60/iA b u t d i d n o t e l i c i t  IOOJIA  NMDA i n j e c t i o n no e f f e c t  either  electrically  Medial  i n t h e second on l o c o m o t o r  locomotion  bird  independently,  (paralyzed)  from while  (34mM/0. 6jxl) h a d  pattern or threshold f o r  stimulated locomotion.  Longitudinal  Infusion stimulation  stimulated walking  F a s c i c u l u s (MLF)  o f NMDA  site  (34mM/0. 4fil)  into  (walking and f l a p p i n g ,  186  a locomotion  promoting  F i g . 26A) i n t o t h e MLF  F i g u r e 25.  Electromyographic records  (EMGs) showing locomotor  a c t i v i t y e l i c i t e d by e l e c t r i c a l s t i m u l a t i o n , NMDA i n j e c t i o n i n t o t h e p o n t i n e r e t i c u l a r A: A l t e r n a t i n g stimulation  f o r m a t i o n (RP).  s t e p p i n g evoked by t h r e s h o l d  electrical  o f RP. The bottom two t r a c e s demonstrate t h e EMG  a c t i v i t y i n the right cranialis  Substance P and  (RITC) and l e f t  (LITC)  muscles, w h i l e the t o p t r a c e s  iliotibialis  (RPECT & LPECT), t a k e n  from t h e p e c t o r a l i s muscles show no a c t i v i t y . B: EMG a c t i v i t y demonstrating only a l t e r n a t i n g hindlimb stepping i n the b i r d following  i n j e c t i o n o f Substance P i n t o t h e same s i t e . The  r h y t h m i c p a t t e r n o f EMG a c t i v i t y seen i n t h e PECT t r a c e s i s b r e a t h i n g . C: S t e p p i n g and f l a p p i n g a c t i v i t y evoked the  following  i n j e c t i o n o f NMDA i n t o t h e s i t e p r e v i o u s l y i n j e c t e d w i t h  Substance P as shown by t h e EMGs from t h e l e g f l e x o r muscles (ITC  - bottom 2 t r a c e s ) and wing d e p r e s s o r muscles (PECT - t o p 2  traces).  187  A RPECT  i MI  LPECT  i  MI  i i — i  I  ,, i  I  J I  ii^iiiiM)<>i ni ;-|••»>••  RITC  LITC 1 sec  188  RPECT I I I I > »'l I I I I I I I M'tH I I t > I I M I M I I I I I I I I H 1  LPECT  RITC  LITC  189  I  1  2 sec  190  F i g u r e 26. activity  Electromyographic  e l i c t e d by e l e c t r i c a l  into themedial right left  longitudinal  (RPECT) a n d l e f t (LITC)  stepping  electrical  stimulation  right  (ENGs) t a k e n  (RITC) a n d l e f t  paralysis hindlimb  (EMGs) s h o w i n g  stimulation  fasciculus  a n d NMDA  locomotor infusion  (MLF). A: EMGs f r o m t h e  (LPECT) p e c t o r a l i s  and r i g h t  (RITC) a n d  i l i o t i b i a l i s c r a n i a l i s muscles i l l u s t r a t i n g t h e  coactivated  records  records  (ITC)  and f l a p p i n g  (PECT) e l i c i t e d b y  o f t h e MLF. B: E l e c t r o n e u r o g r a p h i c  from the (LITC)  left  p e c t o r a l i s muscle  i l i o t i b i a l i s muscles  demonstrating the a l t e r n a t i n g pattern activity  i n t o t h e same s i t e  elicited  b y i n j e c t i o n o f NMDA  a s i n A.  191  (LPECT) a n d  during  of  x  fictive'  (34mM/0. 4LI1)  1 sec  192  RITC  LITC i  193  i  2 sec  replicably  (4 t i m e s ) e v o k e d  stepping within approximately  bilateral  one m i n u t e p o s t - i n j e c t i o n  8 m i n u t e s i n one a n i m a l  (20mM/0.2jil) i n t o could  ^fictive'  a paralyzed b i r d  be e l i c i t e d by e l e c t r i c a l  which l a s t e d f o r  ( F i g . 2 6B).  from which  stimulation  effects.  194  alternating  NMDA i n j e c t i o n  ^ f i c t i v e ' walking  o f t h e MLF  showed no  DISCUSSION  Neurochemical mid-  injection  into  selected  regions of the avian  a n d h i n d b r a i n w i t h EAA a g o n i s t s , a n t a g o n i s t s a n d S u b s t a n c e  P produced birds.  a variety  o f locomotor  responses  I n t r o d u c t i o n o f the glutamate  glutamate  itself,  elicited  intensity  threshold  i n decerebrate  a g o n i s t NMDA, b u t n o t  locomotion or reduced the current  f o r l o c o m o t i o n when i n j e c t e d  electrical-stimulation  d e f i n e d locomotor  r e g i o n s . The i n d u c e d  l o c o m o t i o n c o u l d be b l o c k e d by t h e i n t r o d u c t i o n antagonist  GDEE i n t o t h e same s i t e .  locomotion  following  will  i t s injection  be d i s c u s s e d f o r e a c h  Substance  from  locomotor  our study w i l l  o t h e r s p e c i e s i n which s i m i l a r  o f the glutamate  P also  elicited  i n t o t h e pons. These  results  r e g i o n a n d an a t t e m p t  be made t o e l u c i d a t e t h e n e u r o a n a t o m i c a l them. The d a t a  into  pathways which  b e compared t o t h a t  will  subserve found i n  i n v e s t i g a t i o n s have b e e n  performed.  Pontobulbar  L o c o m o t o r S t r i p (PLS)  Injection locomotor descending  o f NMDA i n t o t h e PLS, t h e p h y s i o l o g i c a l l y d e f i n e d  r e g i o n which appears trigeminal  1988), e v o k e d  tract  t o be synonymous w i t h t h e  and nucleus  locomotion i nb i r d s .  were h i s t o l o g i c a l l y  identified  (TTD) (Noga e t a l , ,  The e f f e c t i v e  as l y i n g  injection  sites  on t h e d o r s o m e d i a l  b o r d e r between TTD a n d Cnd. T h e s e r e s u l t s  are similar  t o those  f o u n d b y Noga e t a l . , (1988) i n t h e c a t , i n w h i c h i n j e c t i o n o f glutamate  elicited  locomotion or decreased the e l e c t r i c a l  195  threshold  intensity  neuroanatomical locomotion  glutamatergic Hill  connections which subserve  The a v i a n  t h e observed  a r e p r e s e n t l y unknown, b u t i n t h e r a t , EAA  corticofugal  and  n e c e s s a r y t o evoke w a l k i n g .  pathways d e s c e n d i n g input t o t h i s  (1981,  carboxylate),  t o t h e b r a i n s t e m may p r o v i d e  region  1983) d e m o n s t r a t e d  a broad  spectrum  :  (Fagg a n d F o s t e r , 1 9 8 3 ) . that  PDA  Salt  (cis-2,3-piperidine  EAA a n t a g o n i s t  (acts a t a l l  r e c e p t o r t y p e s ) , b u t n o t t h e s p e c i f i c NMDA a n t a g o n i s t , D-a-aminoadipate, but  not noxious  caudalis  could block v i b r i s s a l  thermal  afferent  o f TTD i n t h e u r e t h a n e  however, examine t h e t y p e s to  elicit  above  locomotion  (e.g. p i n n a  and noxious  input t o c e l l s  mechanical  i n the nucleus  a n a e s t h e t i z e d r a t . They d i d n o t ,  o f s t i m u l a t i o n w h i c h have b e e n  shown  i n the decerebrate preparation discussed  stimulation  - Aoki  and M o r i ,  1981).  Although  NMDA r e c e p t o r b i n d i n g s t u d i e s i n mammals show l o w d e n s i t i e s o f NMDA r e c e p t o r s i n t h e r e g i o n o f TTD a n d s u r r o u n d i n g * reticular "there  f o r m a t i o n , Monaghan a n d Cotman  i s a trend f o r motor-associated,  glutamate-using  limbic  p a t h w a y s " . However, that  control  after  from  located,  d e n s i t y o f NMDA  these p r e l i m i n a r y findings, impinging  behaviour.  Why g l u t a m a t e  i n t h e PLS i s unknown, a l t h o u g h  injection,  sites using  i t appears  on NMDA  i n t h e PLS/TTD r e g i o n , may p l a y some r o l e  o f locomotor  effective  ventrally  that  and s e n s o r y - a s s o c i a t e d glutamate  g l u t a m a t e r g i c pathways, p o s s i b l y  receptors  (1985) s u r m i s e  p a t h w a y s t o have a l o w e r  than t h e c o r t i c a l ,  lateral  i n the  itself  was n o t  i t i s possible  that  t h e n e u r o t r a n s m i t t e r i s t a k e n up b e f o r e i t c a n  spread t o a s u f f i c i e n t  number o f n e u r o n s t o e l i c i t  NMDA, on t h e o t h e r hand,  i sless  locomotion.  s u s c e p t i b l e t o removal  196  (Stone  and B u r t o n ,  1988)  therefore exert receptors The  and t h r o u g h d i f f u s i o n  i t s action  (see C h a p t e r s  over a l a r g e r  neuroanatomical  o t h e r EAA  concentrations  group  connections through  of neuronal  o f NMDA i n j e c t e d ,  which  r o l e have y e t t o be  r e c e p t o r t y p e s cannot  be  even  ruled  at the  out,  r e c e p t o r subtypes  determined. as  the  lowest  c o n c e n t r a t i o n s n e c e s s a r y t o e v o k e l o c o m o t i o n , may with other glutamate  may  3 & 4).  NMDA/glutamate s e r v e a l o c o m o t o r Also,  through the t i s s u e ,  cross  react  (H. McLennan, p e r s o n a l  communication). W h i l e Noga e t al. i n t o t h e c a u d a l PLS into  comparable  (1988) f o u n d t h a t  evoked  sites  locomotion i n the cat,  involved  ganglion c e l l s  Substance  stimulus the  bird, for  (Salt  1983).  and H i l l ,  1983)  t o be  Substance  gives rise,  dorsal part  i n part,  in  transmitter f o r review  In t h e c a t , l o c o m o t i o n seen  following a  and t h u s w o u l d a p p e a r  elicited noxious to support  o f l o c o m o t i o n . In t h e  a r e r e q u i r e d t o examine a p o s s i b l e  P i n locomotor  dorsal part  at e l i c i t i n g  PLS/TTD s t i m u l a t i o n - i n d u c e d l o c o m o t i o n i s  studies  C e n t r a l Nucleus,  a  e t a l . , 1985;  i n the sensorimotor i n i t i a t i o n  further  The  appears  P i n j e c t i o n mimics t h a t  hypothesis that  involved  and  injection  injections  P has b e e n l o c a l i z e d  i n pain perception (Kishida  s e e Dubner and B e n n e t t , by  P  i n t h e b i r d were i n e f f e c t i v e  locomotor behaviour. Substance trigeminal  Substance  role  control.  (Cnd)  of the medullary c e n t r a l nucleus t o the r e t i c u l o s p i n a l 197  pathway  (Cnd)  which  descends t o a l l s p i n a l c o r d l e v e l s i n b i r d s  (Cabot e t al., 1982;  Webster and S t e e v e s , 1987). S e l e c t i v e l e s i o n s t u d i e s have demonstrated t h a t t h e r e t i c u l o s p i n a l pathway p l a y s a major r o l e i n the descending c o n t r o l o f locomotion i n a l l  vertebrates  s t u d i e d (Sholomenko and S t e e v e s , 1987; f o r r e v i e w see G r i l l n e r , 1976). I n b i r d s , t h e i n f u s i o n o f t h e g l u t a m a t e r g i c a g o n i s t NMDA i n t o Cnd evoked locomotor b e h a v i o u r which was b l o c k e d by t h e a n t a g o n i s t GDEE. The e f f e r e n t c o n t r i b u t i o n o f Cnd t o t h e r e t i c u l o s p i n a l pathway and i t s importance t o t h e d e s c e n d i n g c o n t r o l o f l o c o m o t i o n i n t h e b i r d and o t h e r s p e c i e s has been discussed previously  (See C h a p t e r s 1 & 2 ) . However, no p r e v i o u s  i n j e c t i o n s o f g l u t a m a t e a g o n i s t s i n t o t h i s r e g i o n have been r e p o r t e d . More m e d i a l i n j e c t i o n s o f glutamate and h o m o c y s t e i c a c i d i n t o t h e g i g a n t o c e l l u l a r t e g m e n t a l f i e l d have been r e p o r t e d t o i n d u c e l o c o m o t i o n i n t h e c a t (Noga e t al.,  1988). I n t h e  lamprey, i n t e r n e u r o n s c o n t a i n i n g e x c i t a t o r y amino a c i d s have been i d e n t i f i e d as s p e c i f i c a l l y i m p i n g i n g upon r e t i c u l o s p i n a l neurons which a r e i n v o l v e d i n t h e d e s c e n d i n g c o n t r o l o f locomotion  (Dubuc e t al.,  1988). Furthermore, Dubue and  co-workers  (Dubuc e t al.,  1988) have e s t a b l i s h e d t h e presence o f  NMDA r e c e p t o r s on lamprey r e t i c u l a r f o r m a t i o n neurons. I n a d d i t i o n , t h e s e EAA c o n t a i n i n g i n t e r n e u r o n s r e c e i v e t r i g e m i n a l , v e s t i b u l a r and a s c e n d i n g s p i n o b u l b a r pathways i n p u t al.,  (Dubuc e t  1988). Whether comparable i n t e r n e u r o n s e x i s t i n b i r d s  remains t o be d e t e r m i n e d . Receptor b i n d i n g s t u d i e s i n t h e r a t (Monaghan and Cotman, 1985) r e p o r t low l e v e l s o f NMDA/glutamate r e c e p t o r s i n t h e h i n d b r a i n r e t i c u l a r f o r m a t i o n . Low l e v e l s o f r e c e p t o r do n o t , 198  however, p r e c l u d e a m o d u l a t o r y r o l e (Monaghan a n d Cotman, forebrain region  structures  i n mammals  1 9 8 3 ) . I t i s unknown a t t h i s  to reticular  i n mammals a l s o  number o f n e u r o a n a t o m i c a l  region  retrograde  f o r m a t i o n EAA pathways  e x i s t i n b i r d s . However, a transport  a variety of locomotor-related  which c o u l d  from  w h i c h have b e e n shown t o i m p i n g e on t h i s  time whether t e l e n c e p h a l i c  established  neurotransmitter  1985) i n t h e c o n t r o l o f l o c o m o t i o n  (Fagg a n d F o s t e r ,  comparable t o those  for this  studies  afferents  a l s o be t h e s o u r c e o f EAA i n p u t  have  to this  t o Cnd ( s e e  C h a p t e r s 3 & 4) . The  above r e s u l t s , g a t h e r e d  of  species,  in  the c o n t r o l o f locomotion  structures.  strongly  implicate  Furthermore,  a p p e a r s t o be i n v o l v e d glutamatergic  Central  an e x c i t a t o r y  from r e t i c u l a r  formation  l o c a t i o n o f glutamate  on r e t i c u l o s p i n a l n e u r o n s ,  r e m a i n s t o be  elucidated.  N u c l e u s , v e n t r a l p a r t (Cnv)  S i m i l a r t o Cnd, n e u r o n s l o c a l i z e d w i t h i n portion  and  Cnv g i v e  rise  to a  o f t h e descending r e t i c u l o s p i n a l p r o j e c t i o n which i s  essential birds  subtype  i n t h i s c o n t r o l . However, t h e  pathways and e x a c t  or both,  range  r o l e f o r glutamate  t h e g l u t a m a t e NMDA r e c e p t o r  i n v o l v e m e n t , be i t d i r e c t l y interneurons  from a b r o a d p h y l o g e n e t i c  f o r the i n i t i a t i o n  (Webster a n d S t e e v e s ,  other  species  of t h i s region  (Grillner,  elicits  and maintenance o f l o c o m o t i o n i n  1987; Sholomenko a n d S t e e v e s , 1987) 1985). F o c a l  locomotion  electrical  stimulation  i n a wide r a n g e o f s p e c i e s  (Steeves e t a l . , 1986). P r e v i o u s p a p e r s i n t h i s s e r i e s  199  have  established that integratory  Cnv, l i k e  and descending  sensory and c e n t r a l l y In t h i s Cnv  study,  elicited  Garcia-Rill found t h a t  output  generated  injection  and Skinner  formation e l i c i t e d  a s an  centre for a variety of  locomotor  related  inputs.  o f NMDA, b u t n o t g l u t a m a t e ,  (1987a) a n d Noga e t al.  infusion  into the medial  locomotion or decreased  threshold  (Garcia-Rill  NMDA i n an a t t e m p t  One p o s s i b l e  described produced  to specify  reticular  electrical  and S k i n n e r ,  1 9 8 7 a ) . We  t h e r e c e p t o r type  d i f f e r e n c e between o u r r e s u l t s  i n cat i s the longevity b y NMDA i n j e c t i o n .  o f NMDA v e r s u s g l u t a m a t e therefore,  Both  (1988) have  u n d e r l y i n g t h e p r o d u c t i o n o f l o c o m o t i o n by t h e e x c i t a t o r y acids.  into  i n t h e c a t , a l t h o u g h i n some c a s e s t h e  b e h a v i o u r was s h o r t - l i v e d utilized  to function  l o c o m o t i o n w h i c h was b l o c k e d b y GDEE i n f u s i o n .  glutamate  stimulation  Cnd, a p p e a r s  o f locomotor  The a p p a r e n t  may r e s u l t  increased efficacy,  amino  and those  behaviour  longer l a s t i n g  action  from t h e s l o w e r u p t a k e , a n d  o f NMDA  (Stone a n d B u r t o n ,  1988).  L i k e Cnd, t h e s o u r c e s o f g l u t a m a t e r g i c i n p u t t o Cnv r e m a i n t o b e c h a r a c t e r i z e d . However, EAA p r o j e c t i o n s t o Cnv may a r i s e from more r o s t r a l reticular  (Dubuc e t a l . , 1988; F a g g a n d F o s t e r , 1983). The  o f glutamate  receptor p r o f i l e physiological  neurochemical bird  neuroanatomical,  data f o r b i r d s  role  f o r m a t i o n neurons  1988),  (e.g. t e l e n c e p h a l o n ) , g l u t a m a t e r g i c  f o r m a t i o n i n t e r n e u r o n s and a s c e n d i n g s p i n o b u l b a r  projections paucity  structures  n e u r o t r a n s m i t t e r and  and o t h e r s p e c i e s l e a v e s t h e  for glutamatergic control  of reticular  u n r e s o l v e d . However, combined d a t a  stimulation  a n d mammal  studies  i n lamprey  (Garcia-Rill  200  from  (Dubuc e t  al.,  e t a l . , 1985; G a r c i a - R i l l  and  Skinner,  excitatory  1987a; Noga et al., 1988) s u g g e s t  role  f o r glutamate  locomotion-related  Pontine R e t i c u l a r  Focal reticular  reticular  Steeves,  nuclei  that  locomotion  pathway  1987) I n a d d i t i o n ,  such  sources  Steeves,  including  nuclei  (Hunt  i n p u t from  T T D , tectum,  from  thepontine r e t i c u l a r  p o s i t i o n t o r e g u l a t e motor  locomotor to the  rat  infusion  behaviour  impinge  e t al., 1982;  a wide v a r i e t y  Wold, a  1978;  as i n o f motor  Cnv, Cnd a n d Webster and  neuroanatomical  f o r m a t i o n i s i n an i d e a l  of electrically  stimulated  o f NMDA i n t o t h e v e n t r a l RP e l i c i t e d i n several  a n i m a l s . EAA p a t h w a y s a r e known forebrain  (Fagg a n d F o s t e r , 1983) a n d N M D A - s e n s i t i v e i n t h e pons o f t h e r a t  1 9 8 5 ) . Our d a t a s u g g e s t the b i r d .  related  formation  cerebellum,  on t h e p o n t i n e tegmentum from  have been l o c a l i z e d  Webster  control.  Following the establishment locomotion,  t o a component o f t h e  (Cabot  e t a l . , 1977;  bird  tracing  RP p r o j e c t s t o m o t o r  i n p r e p a r a t i o n ) . Thus,  viewpoint,  i nthe decerebrate  i n p r e p a r a t i o n ) . In b i r d s ,  mammals, RP r e c e i v e s a f f e r e n t  vestibular  pontine  a s T T D a n d more c a u d a l r e t i c u l a r  (Webster a n d S t e e v e s ,  related  o f the v e n t r a l  RP g i v e s r i s e  reticulospinal  structures  structures.  ( S t e e v e s e t al., 1 9 8 6 ) . N e u r o a n a t o m i c a l  s t u d i e s demonstrate  and  formation  stimulation  formation e l i c i t s  descending  i nthecontrol of  F o r m a t i o n (RP)  electrical  preparation  an i m p o r t a n t  that  structures i n binding  (Monaghan a n d Cotman,  s i m i l a r NMDA b i n d i n g s i t e s  However, i t h a s y e t t o be d e t e r m i n e d  201  sites  exist i n  w h e t h e r t h e EAA  projections  arise  from t h e f o r e b r a i n ,  pontine interneurons,  a s c e n d i n g i n p u t s from b r a i n s t e m / s p i n a l c o r d o r o t h e r Our  results  under  suggest that pontine r e t i c u l a r  glutamatergic excitatory Interestingly,  weak b i l a t e r a l significantly  injection  o f Substance  walking behaviour which  (personal  communication)  fibres  l o c a l i z e d w i t h i n t h e paramedian  Substance behaviours  P has i n t h e c o n t r o l  t o be  i n t o t h e same  site.  d e s c r i b e s Substance P - c o n t a i n i n g  formation near t h e v e n t r a l m i d l i n e . Thus,  P i n t o RP p r o d u c e d  appeared  e n h a n c e d b y NMDA i n f u s i o n  i s unspecified.  f o r m a t i o n neurons a r e  control.  Reiner  however,  regions.  pontine  The o r i g i n  speculation  o f these  fibres,  on t h e r o l e  or modulation  i n thepontine r e t i c u l a r  reticular  which  o f locomotor  f o r m a t i o n w o u l d be  premature.  Mesencephalic R e t i c u l a r  F o r m a t i o n (MRF)  Two l o c o m o t i o n - e v o k i n g e l e c t r i c a l been p r e v i o u s l y Chapter site  second,  more m e d i a l  site,  formation v e n t r o l a t e r a l  t o tectum,  The more  layers  (Hunt  high cervical  (see C h a p t e r  lateral  2, F i g u r e 1 ) . A mesencephalic  t o t h e r e d nucleus and medial  lenticularis  1 ) . The mMRF r e c e i v e s  t h e deep t e c t a l  1987b),  i s found i n t h e medial  t o t h e n u c l e u s o f t h e ansa Figure  have  i n close proximity to the i n t e r c o l l i c u l a r  (ICo) o f t h e a v i a n t e c t u m  reticular  sites  i n t h e a v i a n m e s e n c e p h a l o n (See  2 a n d Sholomenko a n d S t e e v e s ,  i ssituated  nucleus  described  stimulation  (mMRF)  ( s e e C h a p t e r 2,  a major a f f e r e n t p r o j e c t i o n e t a l . , 1977) a n d s e n d s  spinal  c o r d and medial  202  from  efferents  medullary  reticular Steeves,  formation  i n preparation).  hodological region  (Reiner  These e l e c t r o p h y s i o l o g i c a l and  considerations,  as an a v i a n  Garcia-Rill  therefore,  equivalent  and Skinner  l i m i t e d by t h e apparent  1982; Webster and  and K a r t e n ,  possibly implicate  o f t h e mammalian MLR d e s c r i b e d by  (198 6).  However, t h i s  l a c k o f an a v i a n  equivalency i s  equivalent  mammalian a c e t y l c h o l i n e - c o n t a i n i n g PPN n e u r o n s Taccogna,  i n preparation).  this  Controversy  still  of the  (Steeves and  e x i s t s as t o  w h e t h e r t h e c h o l i n e r g i c PPN n e u r o n s a c t u a l l y u n d e r l i e t h e effects  o f MLR s t i m u l a t e d  1987,  al.,  1988),  cytoarchitectonic,  locomotion.  cytochemical  pedunculopontine nucleus  was  not part  and h o d o l o g i c a l  i n the rat, postulated  termed t h e midbrain extrapyramidal  recording,  neurochemical  electrically one  animal.  found t h a t threshold  stimulation w i l l  that  alleviate  a region  Only a complete  intracellular this  t h e PPN  profile  of intracellular dye i n j e c t i o n and controversy.  s t u d y , NMDA was f o u n d t o d e c r e a s e t h e t h r e s h o l d stimulated  for  l o c o m o t i o n when i n f u s e d i n t o t h e mMRF i n  S i m i l a r l y , i n the cat,  Garcia-Rill  e t al.  (1985)  g l u t a m a t e i n f u s i o n i n t o t h e PPN/mMLR d e c r e a s e d t h e for electrically  isolation,  elicit  found that  glutamate  locomotor a c t i v i t y  stimulated  locomotion. injection  l o c o m o t i o n b u t d i d not, i n  Mogenson a n d B r u d z y n s k i i n t o t h e PPN/MLR  i n the freely  apparent discrepancy those  area.  p o s s i b l y b a s e d on a c o m b i n a t i o n  immunohistochemistry,  In t h i s  relationships of  o f t h e MLR a n d s u b s t i t u t e d i n i t s p l a c e  region,  (Rye e t  f o l l o w i n g a thorough examination o f the  the  of t h i s  Rye a n d c o - w o r k e r s  increased  moving r a t . Reasons f o r t h e  between t h e f i n d i n g s i n b i r d  found i n r a t a r e p r e s e n t l y  (1986)  and c a t v e r s u s  n o t known, a l t h o u g h v a r i a t i o n  203  in the spatial regions  distribution  i n these species  may a c c o u n t  w i t h i n t h e locomotor f o r some o f t h e d i f f e r e n c e s  1986). In combination with  (Mogenson a n d B r u d z y n s k i , from c h o l i n e r g i c i n j e c t i o n the  of cells  studies discussed  congruence o f those data  our data  i n C h a p t e r 3, and  i n the b i r d with  those  mammals, i t a p p e a r s p o s s i b l e t h a t  avian  exist  be r e q u i r e d t o l e n d  i n b i r d s . Further  strength  Medial  to this  s t u d i e s demonstrated that  decerebrate  previously a  neurochemical  region  bird,  also e l i c i t e d  although only  projections.  which contains Thus,  into this  injected site  region  localized al.,  locomotion i n  i n one a n i m a l . A s d i s c u s s e d  a variety of intranuclear  neurochemical  elicited  l o c o m o t i o n . However,  i n close proximity t o  a n d may be a c t i v a t e d by  (Dube a n d P a r e n t ,  region  neurochemical  1 9 8 1 ) . Whether t h e s e a v i a n i spresently  f r o m mammalian s p e c i e s i n this  as  neurons which s t a i n p o s i t i v e l y f o r  a l s o p o s s e s s EAA r e c e p t o r s of reports  The i n j e c t i o n  repeatable  a c e t y l c h o l i n e s t e r a s e have b e e n l o c a l i z e d  injection  levels.  i t was s u r p r i s i n g t h a t  serotonin-containing  the  (carbachol)  ( C h a p t e r s 2 & 3 ) , t h e MLF i s g e n e r a l l y r e c o g n i z e d  fibre tract  injection  and  l o c o m o t i o n c o u l d be  o f t h e MLF a t p o n t o m e d u l l a r y  o f NMDA i n t o t h i s the  greater  F a s c i c u l u s (MLF)  e l i c i t e d b o t h by e l e c t r i c a l stimulation  o f t h e MLRs  hypothesis.  Longitudinal  Previous  study w i l l  equivalents  found i n  neurons  unknown, b u t a v a r i e t y  do n o t r e p o r t  EAA r e c e p t o r s  (Monaghan a n d Cotman, 1 9 8 5 ; Monaghan e t  1 9 8 5 ; Greenamyre e t a l . , 1 9 8 4 ) .  204  At present,  t h e r e f o r e , EAA  excitation  o f locomotion  neuroanatomical locomotion future  substrate.  i nthis  region,  In t h i s  The r e s u l t however,  study,  direct  at e l i c i t i n g  receptor  subtypes i n the  according kainate  to their  and q u i s q u a l a t e  receptor  cross  receptors receptor,  at three  (for review,  (D. Magnusson, p e r s o n a l  proposed  are c l a s s i f i e d  for the agonists  the with  agonist the  f o r each  o t h e r two  c o m m u n i c a t i o n ) . A t t h e NMDA  NMDA h a s b e e n f o u n d t o b e 10-1000 t i m e s more  than glutamate and i s r e l a t i v e l y (Watkins a n d O l v e r m a n , of preparation glutamate  a n d may r e f l e c t  suggest t h a t t h e s i t e  postsynaptic  specific  1 9 8 7 ) . The p o t e n c y  (fast) uptake  ( f o r review,  NMDA,  s e e S t o n e a n d B u r t o n , 1988/  although  r e a c t s t o some e x t e n t  b y GDEE i n f u s i o n  different  affinity  regions.  glutamate has been  CNS. The r e c e p t o r s  1987),  locomotor  c o u l d be b l o c k e d  differential  Watkins and Olverman,  action  for  locomotion i n  avian  The n e u r o t r a n s m i t t e r  d e m o n s t r a t e d t o be e f f e c t i v e  and  suggests p o s s i b i l i t i e s  i n t r a c e r e b r a l i n f u s i o n o f NMDA, b u t  t h e locomotion  i n t o t h e same s i t e .  results  o f NMDA i n j e c t i o n - i n d u c e d  e l e c t r o p h y s i o l o g i c a l ^ defined  In some c a s e s ,  versus  l a c k s even a p u t a t i v e  Considerations  glutamate, proved e f f e c t i v e  several  type  site  study.  Pharmacological  not  from t h i s  potent  for i t s receptor i s dependent  t h e r a t e o f NMDA  (Stone a n d B u r t o n ,  on t h e  (slow)  1988).  o f NMDA a c t i o n may be b o t h s e e Stone and B u r t o n ,  Recent pre-  1 9 8 8 ) . The  o f NMDA i s complex a n d i n v o l v e s a magnesium a n d v o l t a g e  dependent  increase  i n membrane p e r m e a b i l i t y p r o b a b l y  205  t o calcium  and  sodium i o n s . T h i s  i sdistinct  from t h e a c t i o n o f t h e  non-NMDA r e c e p t o r s  (e.g.q u i s q u a l a t e  activation  i n a voltage-independent  results  c o n d u c t a n c e m e d i a t e d by sodium direct zinc,  l i n k t o ionophore kainate  GDEE, u t i l i z e d originally  study  r e s p o n s e p o t e n t i a t e d by o r v i a an i n t r a c e l l u l a r (for review,  see Choi,  a s a g l u t a m a t e a n t a g o n i s t , was  found t o decrease neuronal  sensitivity  over aspartate  receptors  a t glutamate (Haldeman a n d  (1972), GDEE h a s b e e n d e m o n s t r a t e d t o b l o c k  glutamate receptor quisqualate  subtypes,  receptor  but with  1987; S t o n e a n d B u r t o n ,  above g l u t a m a t e p h a r m a c o l o g y  problems i n a s s e s s i n g t h e exact responsible locomotion  for activating elicited  injection point  physiological  communication),  type  a l l three  efficacy  at the  receptors  1988).  illustrates  the inherent  and l o c a t i o n o f r e c e p t o r s  (or b l o c k i n g )  neurons i n v o l v e d i n  b y NMDA i n f u s i o n . The NMDA c o n c e n t r a t i o n s a t (see T a b l e  concentrations,  glutamate receptor  greater  t h a n a t t h e NMDA a n d k a i n a t e  (Watkins a n d O l v e r m a n ,  the  - fast  1 9 7 2 ) . S u b s e q u e n t t o t h e f i n d i n g s o f Haldeman a n d  McLennan  The  i n membrane  1988).  i nthis  receptors p r e f e r e n t i a l l y McLennan,  (quisqualate  (quisqualate)  & Stone and Burton,  increase  ( q u i s q u a l a t e and k a i n a t e  n o t p o t e n t i a t e d by z i n c )  second messenger system 1988  a n d k a i n a t e ) , whose  subtypes  although  3 a n d r e s u l t s ) were h i g h e r and probably  (D. Magnusson,  than  activated a l l three personal  t h e NMDA c o n c e n t r a t i o n ,  following  diffusion  i n t o t h e t i s s u e s , w o u l d p r e s u m a b l y have d e c r e a s e d  it  throught  spread  t h e CNS t i s s u e .  determine which type(s) the  present  as  I t i s not possible t o  o f g l u t a m a t e r e c e p t o r was a c t i v a t e d i n  experiments. Hopefully,  206  future avian  studies  that  identify  the  subtypes w i l l u n d e r l i e the  neuroanatomical assist observed  location  i n determining results.  of glutamate  which p o s s i b l e r e c e p t o r s  Future  s p e c i f i c NMDA r e c e p t o r a n t a g o n i s t s ,  studies u t i l i z i n g  such  (AP5)  1987), may  regard.  useful in this  207  more  as  2-amino-5-phosphonopentanoic a c i d a l s o be  receptor  (Watkins and  Olverman,  CHAPTER 6  AVIAN LOCOMOTOR PATTERNS IN THE ABSENCE OF PHASIC AFFERENT INPUT - THE 'FICTIVE' PREPARATION  208  INTRODUCTION  In v e r t e b r a t e s , locomotion brain  both the i n i t i a t i o n  and ongoing c o n t r o l o f  a r e d e p e n d e n t upon a h i e r a r c h i c a l  and s p i n a l c o r d n e u r a l  organization of  networks. These c i r c u i t s ,  a r e m o d u l a t e d by p e r i p h e r a l a f f e r e n t f e e d b a c k d u r i n g and  t h e i n t e r a c t i o n between t h e two i s r e s p o n s i b l e  production  o f locomotor p a t t e r n  McClellan,  198 6 ) . P r e v i o u s  b i r d s possess brainstem analogous t o those  Cate,  I960,  f o r normal  avian  1985;  s t u d i e s have d e m o n s t r a t e d  and s p i n a l c o r d  locomotor  and l o w e r  that  networks  vertebrates  1982; S t e e v e s e t a l . , 1986, 1987a,b; Ten  1 9 6 2 ) . T h e s e n e t w o r k s i n c l u d e : 1) s p i n a l c o r d  ^pattern generators', supraspinal Hollyday,  locomotion  ( f o r reviews see G r i l l n e r ,  found i n h i g h e r  (Jacobson & H o l l y d a y ,  i n turn,  input,  which i n t h e absence o f d e s c e n d i n g  can produce  x  s p i n a l stepping'  1982; Sholomenko & S t e e v e s ,  l;  (Jacobson &  1987; t e n C a t e , 1960,  1962), 2) d e s c e n d i n g p a t h w a y s p r o j e c t i n g t h r o u g h t h e ventrolateral locomotion  funiculi  d i s c r e t e brainstem  walking  are e s s e n t i a l f o r i n i t i a t i n g  and o r i g i n a t e i n t h e h i n d b r a i n  (Sholomenko & S t e e v e s ,  chemically  that  regions,  stimulated  and/or  1987; S t e e v e s  flying  reticular  e t a l . , 1987),  formation a n d 3)  w h i c h when e l e c t r i c a l l y o r  i n a decerebrate  preparation,  (Sholomenko & S t e e v e s ,  evoke  1987a,b, 1988;  S t e e v e s e t a l . , 1987). In t h i s phasic avian  chapter,  a f f e r e n t input  I examine w h e t h e r f o r e l i m b  hindlimb  i s a p r e r e q u i s i t e f o r the production  locomotor patterns  afferent  and  by t h e c e n t r a l n e r v o u s system.  of  Phasic  f e e d b a c k was e l i m i n a t e d t h r o u g h p a r a l y z a t i o n o f t h e  209  animal  and  then brainstem  locomotor  r e g i o n s were s t i m u l a t e d i n  the decerebrate b i r d while r e c o r d i n g e l e c t r o n e u r o g r a p h i c activity  from  been used  locomotor-muscle  to describe t h i s  with locomotion (Perret My  1972).  results  demonstrate  can be  including: bilateral walking  1)  activity)  elicited  flying  and  The  term  x  fictive'  d u r i n g neuromuscular  that  a l l unparalyzed  (or h o p p i n g ) ,  ( i . e . combined  4) b i l a t e r a l  paralysis  locomotor animal  (out o f p h a s e ) l e g s t e p p i n g ,  jumping  has  of neural a c t i v i t y associated  i n a paralyzed decerebrate  alternating  ( i n phase)  and  type  o r motor output  e t al.,  patterns  nerves.  210  3) c o a c t i v a t e d  lumbar and  ( i n phase) wing  2)  cervical  flapping.  cord  MATERIALS AND METHODS  Surgery  S u r g i c a l p r o c e d u r e s have b e e n p r e v i o u s l y detail  i n C h a p t e r 2. D e c e r e b r a t i o n l e v e l s  non-spontaneous  Brainstem  animals are described  localized  intracerebral  electrical  from a n o n - s p o n t a n e o u s l y  methods, s t i m u l a t i o n p a r a m e t e r s  versus  7.  or chemical s t i m u l a t i o n used t o  of  evoke  locomoting preparation (for  and p r o c e d u r e s , s e e C h a p t e r s  2-5  thesis). After  establishing  and r e c o r d i n g EMG evoked  an optimum b r a i n s t e m s t i m u l a t i o n  activity  f r o m t h e PECT and  locomotion, each animal  Electroneurograms  7 Pekin  (initially  as r e q u i r e d ) and u n i d i r e c t i o n a l  initiated.  ITC m u s c l e s  (17 Canada g e e s e ,  paralyzed with tubocurarine chloride  supplemented was  i n Chapter  r e g i o n s w i t h i n t h e b r a i n s t e m was  locomotion  was  o f spontaneous  Stimulation  Either  this  described i n  signals.  ENG  conclusion  0.15mg/kg; (UDV)  innervating  S i g n a l s were  amplified  r e c o r d e d i n t h e same manner as t h e  r e c o r d i n g s were made d u r i n g  l o c o m o t i o n and EMG t h e r e was  and  ducks)  (ENGs) were r e c o r d e d w i t h  t h e main body o f ITC and PECT m u s c l e s . filtered  during  ventilation  p l a t i n u m hook e l e c t r o d e s p l a c e d on n e r v e s d i r e c t l y  (10,000x),  site  muscle  activity  was  spontaneous  evoked  monitored t o ensure  no movement i n r e s p o n s e t o s t i m u l a t i o n . A t of each experiment,  or  the p o s i t i o n  of the  EMG  that  the  micropipette  tip  was  direct  marked w i t h an cathodal  current  electrolytic of  3mA  for 5  lesion  made by  seconds at the  passing  a  stimulation  site. Histological previously  identification  described  (Chapter  of  2).  212  stimulation  sites  has  been  RESULTS  Spontaneous  Locomotion  Several high decerebrate birds periods 27A).  of walking  When t h e t r e a d m i l l b e l t  maintained the  i n response  t o a moving t r e a d m i l l was  stopped,  several  showed s p o n t a n e o u s a l t e r n a t i n g  patterns  characteristic  As  f o r one o f t h e s e  of walking animals  (>30min) s p o n t a n e o u s a l t e r n a t i n g s i m i l a r both before  i n both b i r d s preparalyzed  during state  *fictive'  ITC a c t i v i t y  spontaneous  d i d show s h o r t b u r s t s  walking  i n response  maintained  Electrically  Electrical pontobulbar  reduced  relative  fictive'  x  fictive'  to the  locomotion  (5-10 s e c o n d s ) o f  to focal  animals  i n response animals  Xfictive' o f t h e head. In  initiated  electrical  ENGs)  somewhat  The o t h e r 4  l o c o m o t i o n was  lasting  ( F i g . 27B,  t o exteroceptive s t i m u l a t i o n  only i n response locomotor  x  activity  p a t t e r n s were  However, two o f t h e s e  animals  2 birds,  walking  2 of  locomotion).  i n F i g . 27, t h e l o n g  ( F i g . 28, s p o n t a n e o u s ) .  t o t h e moving t r e a d m i l l b e l t .  brainstem  of the birds  (i.e. ^fictive'  ( F i g . 27A, EMGs) a n d a f t e r  d i d not demonstrate  final  belt (Fig.  ITC n e u r a l  p a r a l y z a t i o n . However, t h e s t e p f r e q u e n c y was  the  spontaneous  an u p r i g h t s t a n d i n g p o s t u r e . A f t e r p a r a l y z a t i o n ,  6 animals  shown  (N=6) e x h i b i t e d  and  stimulation of  regions.  Stimulated  Locomotion  stimulation  locomotor  strip,  of brainstem medullary  213  regions including the  reticular  formation,  F i g u r e 27.  Bilateral  alternating walking,activity  spontaneously  locomoting b i r d before  paralyzation.  The t r a n s e c t i o n  post-decerebration saggital  showing  and r i g h t  (B) which  allows  and r i g h t  ITC  (*)  w a l k i n g . B: S u b s e q u e n t  ENG  ITC n e r v e s i n t h e p a r a l y z e d a n i m a l  spontaneous w a l k i n g p a t t e r n  * The i l i o t i b i a l i s c r a n i a l i s mammalian s a r t o r i u s  (dotted line)  from l e f t  spontaneous t r e a d m i l l  from l e f t  (A) and a f t e r  s p o n t a n e o u s l o c o m o t i o n i s shown i n t h e  s e c t i o n . A: EMG t r a c e s  muscles d u r i n g traces  level  in a  activity.  (ITC) m u s c l e  muscle.  214  i s synonymous w i t h t h e  A - PRE-PARALYZED EMG  B_ - PARALYZED ENG LEFT ITC  RIGHT ITC  ^.iii^li! ^iHl^i  . r t , . I ^ I  .iin..^ 1  I  2 sec  215  F i g u r e 28.  Histogram of e l e c t r i c a l  spontaneous step hatch)  and  ^fictive'  frequency during pre-paralyzed  paralyzed  Pre-paralyzed  data  values  stimulation-induced  x  fictive'  (large c r o s s hatch)  have b e e n n o r m a l i z e d  are  shown as  data. Actual pre-paralyzed  (small  to  100%.  % change r e l a t i v e  and  paralyzed  frequencies  f o r each b i r d  from t r i a l s  evoked at b r a i n s t e m  intensities  (numbers i n b r a c k e t s ) .  x  cross  stepping. Paralyzed  to  fictive'  (numbers above r e c o r d )  and•  pre-paralyzed step  were  averaged  stimulation threshold current  216  -i  200  -  175  150 3  £  ZZ  _  w  CO  -  125  fill t I II | • 11 i I II U CNJ  -  100  75-  50-  25-  0  II  m  II  §3  it  m~  %  1:  I  1°  1-2  *—  II«  •11  3  4  5  6  7  8  ANIMAL I (Electrical brainstem stimulation) - PRE-PARALYZED  S3  217  = PARALYZED  1  i 1  C3  2  (Spontaneous)  rostral  pontine  formation in  reticular  and medial  16 a n i m a l s .  formation, mesencephalic  longitudinal  The v a r i e t y  fasciculus  also  on t h e l o c a t i o n  brainstem. for  stimulation Hodos,  muscles  walking Of  by comparing  and nerves,  However,  and  o f the descending  a higher  stimulation  paralyzed states,  observed birds  (1.0Hz±0.18)  condition  stimulation).  Although  the paralyzed bird  (p<0.005) t h a n Electrical  stimulation  (Karten &  paralyzation,  as  p a t t e r n s o f t h e ITC elicited. initiate  i n both  frequency levels  the unparalyzed  of stepping  decreased  i n seven  (1.6Hz±0.27) t o t h e p a r a l y z e d brainstem  t h e mean s t e p p i n g f r e q u e n c i e s o f t h e 2 different  intensity  (ANOVA, p = . 0 7 5 ) , t h e  necessary  t o evoke  (176±25LIA) w a s s i g n i f i c a n t l y  i n the unparalyzed stimulation  characteristically  (TTD)  was r e q u i r e d t o  ( F i g . 28, e l e c t r i c a l  mean t h r e s h o l d s t i m u l a t i o n  intensity  walked  t h e averaged  groups were n o t s i g n i f i c a n t l y  in  moderately  ( F i g .29B).  which  the unparalyzed  firing  intensity  at threshold stimulation  from  nucleus  w a l k i n g p a t t e r n was  following paralyzation the eight animals  at  constant  electrical  (Fig. 29A). A f t e r  alternating  animal,  p a t t e r n was  monopolar  trigeminal  a similar  locomotion  electrode within the  f o r example,  ( 2 5 - 1 0 0 uA),  1967) e v o k e d w a l k i n g  determined  locomotor  I n one a n i m a l ,  weak c u r r e n t s t r e n g t h s  locomotion  of the decerebrate  of the stimulating  However, t h e e l i c i t e d  any g i v e n s i t e .  produced  o f p a t t e r n s i n t h e evoked  depended n o t o n l y on t h e c o n d i t i o n but  reticular  elicited  intensities,  animals  of other  greater  (67±8LIA) .  locomotor  walking behaviour  regions at  lpwer  w i t h recruitment o f wing  i n c r e a s e d . T h i s p a t t e r n i s shown f o r one  218  walking  activity animal  as  Figure  29.  Bilateral  focal  electrical  after  (B)  dotted  the  stimulation  paralyzation.  line  triangle  The  i n the  from l e f t  stimulated  The  medullary  and  of the right  w a l k i n g . B:  ENG  of the  hindbrain  transection  stimulation  transverse  descending t r a c t  traces  a l t e r n a t i n g walking a c t i v i t y  and  level  site,  l e g ITC traces  showing evoked w a l k i n g p a t t e r n s  before  marked by  i n the  219  was  (PLS).  muscles d u r i n g from l e f t  (A)  by and  i s shown by  saggital sections,  t r i g e m i n a l nerve  evoked  and  paralyzed  A:  the  the located  in  EMG  electrically  right bird.  ITC  nerves  A - PRE-PARALYZED EMG «  LEFT ITC  RIGHT ITC  I + M M T ' O T ' M  2 sec  TTD  LEVEL OF DECEREBRATION  STIMULATION SITE  B - PARALYZED ENG LEFT ITC  RIGHT ITC  4+  , n  O  4  nI  < | i » UK  i 2  220  1 sec  s t i m u l a t e d w i t h i n the r e g i o n of the mesencephalic formation  (MRF)  p r i o r to paralyzation  reticular  ( F i g . 30A). At a  s t i m u l a t i o n i n t e n s i t y of 40LIA, walking movements were i n i t i a t e d and i n c r e a s e d i n frequency as i n t e n s i t y was  i n c r e a s e d . When  c u r r e n t i n t e n s i t y reached approximately 90/iA, b i l a t e r a l wing f l a p p i n g was  a l s o observed. The same sequence of events was  observed i n the p a r a l y z e d animal  not  ( F i g . 30B), but c o a c t i v a t i o n of  the nerves from both l e g s and one wing was  observed. As  seen  p r e v i o u s l y d u r i n g walking alone, the e l e c t r i c a l c u r r e n t s t r e n g t h s necessary t o evoke r h y t h m i c a l locomotor a c t i v i t y were at l e a s t two times g r e a t e r i n the p a r a l y z e d versus unparalyzed animal. In-phase  wing f l a p p i n g alone, c h a r a c t e r i s t i c of f l y i n g  behavior, was  a l s o o f t e n e l i c i t e d i n response t o e l e c t r i c a l  s t i m u l a t i o n of s p e c i f i e d brainstem r e g i o n s ( F i g . 31A).  After  p a r a l y z a t i o n , a s i m i l a r p a t t e r n of evoked motor a c t i v i t y c o u l d be recorded from the PECT nerves  ( F i g . 31B). The average c u r r e n t  s t r e n g t h necessary, however, t o evoke paralyzed birds  (155±27/iA) was  x  fictive'  f l y i n g i n the  s i g n i f i c a n t l y g r e a t e r (ANOVA,  p=0.036) than t h a t r e q u i r e d t o i n i t i a t e locomotion i n the unparalyzed b i r d s  (71±26fiA, n=6) ( F i g . 32) . In s p i t e of t h i s  i n c r e a s e d s t i m u l u s i n t e n s i t y , the s i x animals which e l i c i t e d both unparalyzed f l a p p i n g and  Xfictive'  flapping displayed a  s i g n i f i c a n t r e d u c t i o n (ANOVA, p=0.018) i n evoked frequency a f t e r p a r a l y s i s was 1.6Hz±0.2)  initiated  ( F i g . 32).  221  flapping  (from 2.9Hz±0.4 t o  Figure  30.  Co-activation  focal  electrical  after  (B)  dotted  triangle in  the  The  l e g and  stimulation  paralyzation.  line.  of  The  midbrain  of the  stimulation  i n b o t h s a g g i t a l and  medial mesencephalic r e t i c u l a r right  and  ITC  (bottom 2 t r a c e s )  right  stimulation  Pectoralis  (PECT)  showing t r a n s i t i o n  simultaneous w a l k i n g / f l y i n g . (top t r a c e )  and  left  showing c o a c t i v a t e d wing d u r i n g  and  site,  right  sections,  formation.  (top 2 t r a c e s )  muscles d u r i n g  ENG ITC  traces  stimulation  difficulty,  only  from l e f t  of the  paralyzed  a s i n g l e wing t r a c e  n o r m a l l y phase l o c k e d  bilaterally  synchronous d u r i n g  both paralyzed  31).  222  traces  and  left  and  Pectoralis nerves legs  and  animal.  Due  i s shown i n  However, w i n g s a r e  (see F i g u r e  EMG  to  these data.  locomotion  located  electrically  (bottom 2 t r a c e s )  i n the  the  the  was  A:  by  and  i s shown by  from w a l k i n g a l o n e  B:  (A)  marked by  evoked locomotor p a t t e r n s  electrical  recording  level  transverse  and  evoked  midbrain before  transection  from l e f t  to  wing a c t i v i t y  and  actual  A - PRE-PARALYZED  EMG  STIMULATION SITE  LEVEL OF DECEREBRATION  B -PARALYZED ENG  LEFT PECT LEFT ITC RIGHT ITC  m  It  t « i *<••»  H  j 2i»c  223  \  Figure  31.  Bilateral  focal  electrical  after  (B)  dotted  the  The  i n the  dorsal part  formation). during  stimulation  paralyzation.  line.  triangle  synchronous  A:  The  medullary  EMG  electrically  of the  transection  and  and  r i g h t P e c t o r a l i s nerves  the  paralyzed  site,  and  flying.  by  (A)  marked by was  224  the  the located  in  (reticular  r i g h t P e c t o r a l i s muscles B:  ENG  traces  from  showing evoked f l y i n g p a t t e r n s  bird.  and  i s shown by  c e n t r a l nucleus  from l e f t  stimulated  level  evoked  before  saggital sections,  medullary  traces  activity  hindbrain  stimulation  transverse of the  flying  left in  A - PRE-PARALYZED EMG LEFT PECT  RIGHT PECT  1 sec  TTD  OC  V  LEVEL OF DECEREBRATION  STIMULATION SITE  B-PARALYZED ENG LEFT PECT  RIGHT PECT 2 sec  225  Figure  32.  frequency x  Histogram of brainstem during pre-paralyzed  fictive'  (large  been n o r m a l i z e d bird  are  c r o s s hatch) to  shown as  100%.  frequencies  (small c r o s s hatch) flapping.  Paralyzed  % change r e l a t i v e  Actual pre-paralyzed  and  stimulation-induced  paralyzed  (numbers above r e c o r d )  226  values  *fictive'  paralyzed data  have  f o r each  to pre-paralyzed  data.  wingbeat  were a v e r a g e d  evoked at t h r e s h o l d s t i m u l a t i o n i n t e n s i t i e s brackets).  and  Pre-paralyzed  ^fictive'  wingbeat  from  flapping  (numbers i n  I WINGBEAT FREQUENCY  Chemically  Direct  Stimulated  Locomotion  intracerebral  infusion  a g o n i s t s and a n t a g o n i s t s a l s o decerebrate birds 3)  brainstem  reticular  gigantocellularis the  right  33A).  evoked  (see C h a p t e r s  ( l ( j l a t 0.2ml/min/  r e c o r d e d i n more d i s t a l that  restricted  to just  into theventromedial reticularis  alternating bursting  o f locomotor  activity  l e g muscle nerves  activity i n  (e.g.  was a l s o gastrocnemius)  t h e p a r a l y z e d l o c o m o t o r p a t t e r n was n o t the major h i p muscles.  locomotor p a t t e r n s mimicked t h o s e seen electrical  (N =  l e g ITC n e r v e s o f a p a r a l y z e d goose ( F i g .  Carbachol a c t i v a t i o n  indicating  Carbachol i n j e c t i o n  [nucleus  (Rgc)] e v o k e d  and l e f t  locomotion i n paralyzed  3-5).  27mM i n PBS)  formation  of specific neurotransmitter  stimulation  Carbachol-induced  i n response t o f o c a l  o f the b r a i n s t e m both b e f o r e and a f t e r  paralyzation. Injection  o f N-methyl-d-aspartate  (0.4fil a t 0.2jj.l/min, 5 o r 30mM i n PBS) formation  [nucleus c e n t r a l i s medulla  (Cnd)] p r o d u c e d  similar  and p a r a l y z e d b i r d s . left in  and r i g h t  locomotor  unparalyzed b i r d  the  oblongata, pars  responses  reticular  dorsalis  i n both unparalyzed of the  l e g ITC n e r v e s o f a d e c e r e b r a t e p a r a l y z e d goose o r jumping  l o c o m o t o r p a t t e r n was i d e n t i c a l  patterns  into the caudal  F i g u r e 33B shows NMDA a c t i v a t i o n  an i n - p h a s e h o p p i n g  alternating  (NMDA) i n 2 a n i m a l s  after  t o that  an i n t r a c e r e b r a l  (e.g. walking)  c a n be e l i c i t e d  b r a i n s t e m , however,  locomotor p a t t e r n .  and in-phase  observed injection  i na different o f NMDA. B o t h  (e.g. hopping)  by i n t r a c e r e b r a l  injection  i t i snotpresently  228  This  clear  locomotor  o f NMDA i n t o  what  Figure by  Bilateral *fictive'  neurochemical m i c r o i n j e c t i o n  traces A  33.  from t h e l e f t  fictive'  (I.OLII  walking a c t i v i t y  : 0.2Lil/min  p o n s . The s i t e section  and r i g h t  o f carbachol  following  injected  agonist,  glutamatergic  within  thepontine  central  a f t e r i n j e c t i n g NMDA agonist,  nucleus  into the  ( t r i a n g l e ) , as shown i n t h e t r a n s v e r s e  f o r m a t i o n . B: ENG t r a c e s  galloping)  alternating  i n j e c t i o n o f carbachol  gigantocellular  from t h e l e f t  nerves showing synchronous in-phase a c t i v i t y or  elicited  a n d NMDA. A: ENG  ITC n e r v e s showing  : lOOmM) , a c h o l i n e r g i c  A, was l o c a t e d  reticular  hindlimb nerve a c t i v i t y  (0.2fil  into thedorsal  (triangle i n transverse  229  a n d r i g h t ITC  ( ^ f i c t i v e ' hopping  : 20mM) , a  part  o f the medullary  section B).  A - CARBACHOL - PARALYZED ENG LEFT ITC  RIGHT ITC 3  \  sec  TTD  UJ  fl-v Cnd  PaM A CARBACHOL STIMULATION SITE  B NMDA STIMULATION SITE  B - NMDA - PARALYZED ENG LEFT ITC  RIGHT ITC  3 sec  230  determines Steeves,  which p a t t e r n w i l l  i n p r e p a r a t i o n ) . The  both unparalyzed onset  paralyzed)  expressed  time  activity  10-15  was  (Sholomenko & o f NMDA a c t i v a t i o n similar,  with  b e g i n n i n g w i t h i n 2 minutes of  i n j e c t i o n . Locomotion  ceased  course  and p a r a l y z e d a n i m a l s  of locomotor  intracerebral  be  minutes  (both u n p a r a l y z e d  post-injection.  231  and  the the  in  DISCUSSION  The  main f i n d i n g  decerebrate birds  of the present  (i.e. *fictive'  p r o d u c i n g a l l t h e same l o c o m o t o r animals,  study  i s that paralyzed  preparations) are capable of p a t t e r n s as u n p a r a l y z e d  r e g a r d l e s s o f whether t h e ^ f i c t i v e ' (Fig. 27B),  generated:  1) s p o n t a n e o u s l y  electrical  stimulation  ( F i g . 29B,  to direct  intracerebral  chemical  locomotor  regions  (33A,B).  example o f * f i c t i v e ' Furthermore, behaviour  30B,  o r 3)  into  b i p e d a l locomotion  complex a c t i v a t i o n  to focal  i n response  brainstem  To my knowledge, t h i s  the coactivation  networks can a l s o  i n response  31B),  infusion  i s the f i r s t  i n a vertebrate.  o f b o t h modes  of  locomotor  ( F i g . 30A,B)  ( s t e p p i n g and f l a p p i n g )  relatively  2)  locomotion i s  of brainstem  illustrates  and s p i n a l  occur i n t h e absence o f p h a s i c  that  locomotor  peripheral  feedback. It  i s clear  motor a c t i v i t y  from t h e p r e s e n t o b s e r v a t i o n s t h a t  resembling walking  the absence o f p h a s i c p e r i p h e r a l CNS It  and f l y i n g  rhythmic  c a n be e l i c i t e d i n  input, thereby  implicating the  i n g e n e r a t i n g a c o n s i d e r a b l e a r r a y o f a v i a n motor p a t t e r n s . has been argued  that  the ^ f i c t i v e '  response  to focal  infusion  of neurotransmitter related  locomotor  electrical  stimulation  r e g i o n s i s due, i n p a r t ,  pathways t h a t  normally  relay  electrical  stimulation  fictive'  locomotor  or i n t r a c e r e b r a l  chemicals  somatosensory  [ e . g . TTD o r p o n t o b u l b a r  x  232  into  brainstem of central  information during  locomotor  (Noga e t a l . , 1988) activity  observed i n  t o the a c t i v a t i o n  locomotion  this  locomotion  strip  (PLS)  ( F i g . 2 9 ) ] . Thus,  i n p a r a l y z e d animals  may n o t  reflect  an i n h e r e n t  However, t h i s  CNS l o c o m o t o r p a t t e r n  possibility  i s eliminated,  generating  capacity.  at l e a s t f o r avian  w a l k i n g , by t h e p e r s e v e r a n c e o f ^ f i c t i v e '  l e g locomotor  a f t e r p a r a l y s i s i n t h e s p o n t a n e o u s l y moving animal  n o t a c t i v a t e d by p h a s i c In  spite of the capacity  g e n e r a t e l o c o m o t o r rhythm, proprioceptive this  birds,  i t i s important  The  higher  sensory  activation  threshold  input  serves  level.  of the paralyzed  A  b i r d s may  to paralyzation  spontaneous fictive'  frequencies  stimulation walking  precluded  This  suggestion,  spontaneous  locomotion  enough t o a l l o w  during  spontaneous  i n the remaining 4  spontaneous  activity  i s s u p p o r t e d by t h e f i n d i n g t h a t  (non-noxious) c o u l d  i n 2 of the 4 birds that  spontaneous locomotion d u r i n g  this  *fictive'  the activation state of the 2  a n i m a l s was h i g h  following paralyzation.  suggest  of the animal's  walking, while the a c t i v a t i o n l e v e l  ^fictive'  activated.  foractivating  spontaneous p a t t e r n s  I t i s possible that  fictive  exteroceptive  observed  b i r d s might  argue a g a i n s t  exhibited  elicited  was r e d u c e d t o l e v e l s t h a t  of  stimulation  t o lower t h e t h r e s h o l d  2 o f the 6 animals that  paralyzation.  One f a c e t o f  While t h e occurrence o f spontaneous  walking i n paralyzed  prior  that  a n i m a l s when l o c o m o t i o n was f i n a l l y  movement by i n c r e a s i n g t h e o v e r a l l g a i n  only  t o note  t o a c t i v a t e locomotion i n the paralyzed  i n a d d i t i o n t o t h e lower locomotor  the paralyzed  that  o f t h e CNS t o i n d e p e n d e n t l y  f e e d b a c k does a l t e r motor p a t t e r n .  required  (1988)  input.  i n f l u e n c e was e v i d e n c e d by t h e g r e a t e r  intensity  in  sensory  ( F i g . 27B),  by Noga e t al.  where t h e s o m a t o s e n s o r y p a t h w a y s d e s c r i b e d are  activity  elicit  short  d i d not e l i c i t  paralysis. A further piece of  233  bouts  evidence,  namely, t h e  indirectly  supports  increase the here, at  rare occurrence  the  argument t h a t  1967), t h a t t h e than that often  afferent  feedback  output  than that  walking  i s present,  i n the  cat  et a l . ,  occur  elicit  1966,  activation i s greater to  170/nA i s  a n d / o r w i n g f l a p p i n g when  similar  sufficient paralyzed  stimulation,  i n determining  although  to a c t i v a t e the  forelimb  bird.  "activation level",  remains u n c l e a r .  required to  (Shik  degree t o which a f f e r e n t input  input plays  to  presented  Thus, where s t i m u l a t i o n up  legs, i s rarely  establishing this afferent  greater  seen i n the  to e l i c i t  pattern generators The  as  for hindlimbs.  activating  From r e s u l t s  threshold for forelimb  sufficient  serves  f l a p p i n g i s c o n s i s t e n t l y observed to  stimulation intensities i t appears,  flying,  afferent input  animals a c t i v a t i o n l e v e l .  where b i l a t e r a l  walking,  of f i c t i v e  i s important  and,  the  in  i n t u r n , the  frequency  of  locomotor  However, s t u d i e s i n w h i c h t h e  input  i s c o n t r o l l e d may  help  Afferent  input  c o u l d be  f o r example, by a l t e r n a t e l y  lifting  the  legs of the  appropriate  extensor  p r o v i d i n g the  animal  phase o f  b i r d with  preparation  peripheral  and  varying  c o u l d be  f e e d b a c k on  electrically  increase the  utilized  In c o n c l u s i o n , , t h i s  of avian  thereby feedback.  both i n the  the  effects  spontaneous  of of  and  preparations. study  has  demonstrated t h a t the  nervous system p o s s e s s e s n e u r a l networks which can wide a r r a y  the  activation level  to explore  of  issues.  during  locomotion,  degrees of sensory  locomotion  stimulated  excursions)  ^fictive'  T h i s paradigm would presumably the  (graded  solve these  degree  afferent  applied,  to  role  locomotor patterns  234  i n the  central  produce  absence  of  a  afferent  feedback. This  importance  of afferent  walking pattern.  feedback  level"  is  to i n i t i a t e  also  greater  l o c o m o t i o n and t h a t , considerably.  235  of a  normal  appears t o lower  o f the animal such t h a t  l o c o m o t o r movements a r e r e d u c e d  a l l u d e d to the  i n the production  Removal o f a l l f e e d b a c k  "activation required  s t u d y , however, has  the  stimulation  once i n i t i a t e d ,  the  CHAPTER 7 TRANSECTION LEVEL DETERMINES SPONTANEOUS MOTOR ACTIVITY IN THE DECEREBRATE AVIAN PREPARATION  INTRODUCTION  In v e r t e b r a t e s , s e l e c t i v e b r a i n t r a n s e c t i o n levels  of the n e u r a x i s y i e l d s v a r y i n g degrees  locomotor Wetzel  activity  and  (for review  S t u a r t , 1976;  see  S h i k and  Armstrong,  summarizes t h e m o t o r c a p a b i l i t i e s  variety  w i t h minor v a r i a t i o n ,  Garcia-Rill, produce  rats  Orlovsky,  (Magnus, 1924),  transection  and  ability  a c u t e p r e p a r a t i o n ( t r a n s e c t i o n B and  S h i k and  Orlovsky,  to  1976). N e u r a l  spontaneous locomotor  behaviour  region  (SLR)  p o s t e r i o r hypothalamic neurons  ( W e t z e l and  Our  nuclei  1986,  this  thesis;  of  subthalamic  subthalamic  have d e m o n s t r a t e d  o f b o t h h i g h e r and  1987;  in this  neurons,  and p o s t e r i o r t h a l a m i c m i d l i n e  substrates f o r locomotion  al.,  found  S t u a r t , 1976).  studies with birds  a variety  contained and S t u a r t ,  initiation  i n c l u d e the  (Waller,1940),  (Wetzel  structures  versus  C i n Figure  sparing of structures  r e s p o n s i b l e f o r the  locomotor  These  rabbits  s p o n t a n e o u s l o c o m o t i o n between t h e p r e m a m m i l l a r y  r e g i o n w h i c h c o u l d be  in  briefly  Skinner  animal's  w i t h i n t h e p r e s e r v e d wedge o f n e u r a l t i s s u e  neural  1  1976;  shown i n F i g u r e 1.  (Woods, 1964;  have b e e n a t t r i b u t e d t o t h e  1976;  spontaneous  are e q u a l l y a p p l i c a b l e to a  1 9 8 4 ) . D i f f e r e n c e s i n an  postmammillary 1)  and  different  of cats following  o f mammals i n c l u d i n g dogs  ( H i n s e y e t a l . , 1930)  of  1986). T a b l e  of the neuraxis at the v a r i o u s l e v e l s results,  at  Sholomenko and  that  appear s i m i l a r lower  M c C l e l l a n , 198 6 ) , t h u s  237  avian  to those  vertebrates  Steeves,  the  1987a,b;  found  (Steeves  et  Sholomenko,  i m p l y i n g a h i g h degree  of  TABLE 4. TRANSECTION LEVEL THALAMIC F i g 1-Line A  ANIMAL  CAT  ACUTE PREPARATION  SPONTANEOUS LOCOMOTION SPONTANEOUS LOCOMOTION (MAGNUS. (HINSEY (SHIK  1924) ET  ET  AL,  AL.,  -STIMULATION SLR  ELICITS  (SHIK  PRECOLLICULAR PREMAMMILLARY  CAT  ET  (HINSEY  ET  ET  MLR  (BARD  AND  1966)  MACHT,  1958)  OR  WALKING 1966A)  AL.,  AL.,  -STIMULATION (SHIK  CAT  OF  AL.,  ELICITS  PRECOLLICULAR POSTMAMMILLARY F i g 1-Line C  (DENNEY-BROWN,  1930) 1966)  SPONTANEOUS LOCOMOTION SPONTANEOUS LOCOMOTION (SHIK  F i g 1-Line B  CHRONIC PREPARATION  1930)  OF  AL.,  1930)  MLR  AL.,  1966)  NO SPONTANEOUS LOCOMOTION (SHIK  ET  LOCOMOTION  ET  (HINSEY  (HINSEY  1966)  ET  ET  SPONTANEOUS LOCOMOTION (BARD  AL.,  AL.,  1930)  AND  MACHT,  (VILLABLANCA,  1958)  1962)  1966,  1 967 ) -STIMULATION ELICITS (SHIK  ET  OF  MLR  LCOMOTION AL.,  1966,  1 967 )  PRECOLLICULAR POST-OCCULOMOTOR NERVE F i g 1-Line D  CAT  MIDCOLLICULAR PRE-OCCULOMOTOR NERVE F i g 1-Line E  CAT  NO SPONTANEOUS LOCOMOTION (BARD  AND  MACHT,  1958)  LOCOMOTION IN RESPONSE TO STRONG EXTEROCEPTIVE STIMULATION (BARD  NO SPONTANEOUS LOCOMOTION (BARD  AND  MACHT,  1958)  MACHT,  1958)  ALTERNATING LIMB MOVEMENTS IN AN ANIMAL WHICH IS LYING PRONE (BARD  238  AND  AND  MACHT,  1958)  F i g u r e 34. Diagram of a s a g g i t a l s e c t i o n through the c a t b r a i n s t e m showing n e u r a x i s t r a n s e c t i o n l e v e l s and locomotor s i t e s important f o r the study of locomotor c o n t r o l . T r a n s e c t i o n l e v e l s are d e s i g n a t e d by l e t t e r s A-E. T r a n s e c t i o n l e v e l : A t h a l a m i c , B - p r e c o l l i c u l a r premammillary (hypothalamic of Hinsey et al., 1930)/ C - p r e c o l l i c u l a r postmammillary, D p r e c o l l i c u l a r post-occulomotor, E - m i d c o l l i c u l a r pre-occulomotor. Locomotor s i t e s i n c l u d e the subthalamic locomotor r e g i o n (SLR) and mesencephalic locomotor r e g i o n (MLR). The hatched l i n e s surrounding RPC and RGC r e p r e s e n t the p o n t i n e and medullary r e t i c u l a r f o r m a t i o n t h a t are thought t o be the major motor i n f o r m a t i o n p r o j e c t i o n systems t o the s p i n a l c o r d . A b b r e v i a t i o n s : CM - mammillary body, CO - o p t i c chiasm, IC i n f e r i o r c o l l i c u l u s , MLR - mesencephalic locomotor r e g i o n , P pons, R - r e d nucleus, RGC - medullary g i g a n t o c e l l u l a r r e t i c u l a r nucleus, RPC - caudal p o n t i n e r e t i c u l a r nucleus, SC - s u p e r i o r c o l l i c u l u s , SLR - subthalamic locomotor r e g i o n , T - t r a p e z o i d body, Th - thalamus. I I I - occulomotor nerve. See t e x t f o r a d d i t i o n a l e x p l a n a t i o n . T h i s f i g u r e i s redrawn from: 1) Shik et al., 1968, 2) Orlovsky, 1970a, 3) G r i l l n e r and Shik, 1973 and 4) Wetzel and S t u a r t , 1976.  239  conservation r a n g e . To the  o f motor c i r c u i t r y  f u r t h e r t h i s c o m p a r i s o n and  structures  locomotion,  we  required  as  f o r the  on  a broad i n an  initiation  have e x a m i n e d t h e  brain transection Our  across  phylogenetic  attempt of  e f f e c t s of d i f f e r e n t l e v e l s  acute avian  i n mammals, a n i m a l s w i t h a r o s t r a l  transection  (post-habenular/preoptic) w h i l e more c a u d a l  (post-habenular/postoptic) Diencephalic transection  of  spontaneous locomotor c a p a b i l i t y i n b i r d s .  r e s u l t s indicate that  locomotion,  delineate  spontaneous  i n the  neuraxis  to  structures  display  preparation, of  the  spontaneous  transection  eliminates which are  spontaneous  contained  l e v e l s presumably u n d e r l i e  240  any  this  behaviour.  between t h e s e difference.  two  MATERIALS AND METHODS  Surgery  Surgical previously following  a n d EMG/ENG r e c o r d i n g p r o c e d u r e s  described  ( C h a p t e r 2) w i t h t h e e x c e p t i o n  a craniotomy,  along a plane habenular  edge o f t h e o p t i c  to either: chiasm  been d e s c r i b e d i n d e t a i l  from t h e c a u d a l margin o f t h e  1) t h e r o s t r a l  o r 2) t h e c a u d a l  f o r low d e c e r e b r a t e a n i m a l s  this  after  r e c o r d i n g t h e spontaneous e l e c t r o m y o g r a p h i c  and  Chapters  2-5).  s a c r i f i c e d w i t h an i n t r a v e n o u s i n j e c t i o n  animals,  (EMG) a c t i v i t y  the level  Assessment  Two  coronal sections  o f Karten  a n d Hodos  (1967)  (1971).  o f Spontaneous v e r s u s  criteria  were u s e d  non-spontaneous b i r d s . pinch  atlases  i n Chapter  o f d e c e r e b r a t i o n was  by t h e r e c o n s t r u c t i o n o f s e r i a l  according to the stereotaxic Zweers  o f KC1 (2M).  have b e e n d e s c r i b e d i n d e t a i l  with the exception that  determined  and  In high decerebrate  t h e l e g s a n d / o r w i n g s , t h e b i r d s were d e e p l y a n a e s t h e t i z e d  H i s t o l o g i c a l procedures 2,  have  p r e v i o u s l y (Sholomenko a n d S t e e v e s ,  1987;  from  performed  ventrally.  Stimulation procedures  thesis,  that  a s u c t i o n d e c e r e b r a t i o n was  extending d o r s a l l y  nucleus  have b e e n  stimulation  First  following  Non-spontaneous  to distinguish was t h e b i r d ' s removal  241  spontaneous response  from  t o f o o t web  of anaesthetic. Strong  r e f l e x w i t h d r a w a l was common t o a l l b i r d s , however, t h o s e b i r d s r e s p o n d i n g t o web p i n c h w i t h s t e p p i n g motions and/or wing f l a p p i n g met t h e f i r s t c r i t e r i a f o r spontaneous p r e p a r a t i o n s . Second, i f t h e b i r d s a l s o d i s p l a y e d p r o l o n g e d w a l k i n g b e h a v i o u r ( l o n g e r t h a n 1 minute c o n t i n u o u s ) i n response t o t h e t a c t i l e and l e g movement s t i m u l a t i o n produced when t h e t r e a d m i l l was t u r n e d on, t h e y were c o n s i d e r e d  spontaneous.  Animals which d i d not meet t h e above c r i t e r i a were c l a s s i f i e d as non-spontaneous. These a n i m a l s r e q u i r e d e i t h e r e l e c t r i c a l o r neurochemical b r a i n s t e m s t i m u l a t i o n t o e l i c i t locomotor b e h a v i o u r s .  242  RESULTS  Ten animals  (6 Canada geese, 4 Pekin ducks) with  r o s t r a l t r a n s e c t i o n d e p i c t e d i n F i g u r e 35 spontaneous locomotion.  resembling  posture, when the t r e a d m i l l b e l t was was  ( l i n e A) d i s p l a y e d  S e v e r a l of the animals  s i g n i f i c a n t extensor tonus,  the  displayed  t h a t of a s t a n d i n g  m o t i o n l e s s . When the b e l t  t u r n e d on, the l e g s were moved c a u d a l l y and the  animals.  would begin to make a l t e r n a t i n g s t e p p i n g movements (Figure 36A,B). The  s t e p p i n g seldom appeared of s u f f i c i e n t  s e l f - s u p p o r t i n g , although t o t a l f o r c e was  f o r c e t o be  difficult  to  determine. Of the t o t a l of ten spontaneous animals, d i s p l a y e d wing f l a p p i n g behaviour  only one  combined with s t e p p i n g i n  response t o the t r e a d m i l l b e l t s t i m u l a t i o n alone The  f l a p p i n g o c c u r r e d i n short b u r s t s  long)  (Figure 37).  (approximately  and subsided over s e v e r a l hours,  b e l t - s t i m u l a t e d s t e p p i n g continued  bird  10 seconds  even though  f o r s e v e r a l hours.  In the spontaneous b i r d s , t a c t i l e s t i m u l a t i o n of p a r t s of the body other than the f e e t  (e.g. s t r o k i n g around the eye  caudal back region)  i n c r e a s e d the f o r c e of hindlimb  when the animal was  walking.  Similarly,  i f an animal  or  stepping ceased  s t e p p i n g i n response t o the b e l t , t a c t i l e s t i m u l a t i o n would o f t e n r e - i n i t i a t e the s t e p p i n g Two hindlimb  behaviour.  b i r d s which were p a r a l y z e d d i s p l a y e d a l t e r n a t i n g ^fictive'  s t e p p i n g a c t i v i t y i n the absence of  p h a s i c a f f e r e n t input  any  ( t r e a d m i l l b e l t o f f ) from the p e r i p h e r y  243  Figure  35.  which permit decerebrate  Diagram o f the t r a n s e c t i o n l e v e l s  or e l i m i n a t e spontaneous locomotion bird.  0.5mm) s a g g i t a l  The  diagram  section  i s of a near  of the pigeon  1967). L i n e A d e s i g n a t e s t h e allows  of the  spontaneous locomotion  brain  show s p o n t a n e o u s l o c o m o t o r  (lateral  ( K a r t e n and  Hodos,  of section  i n the decerebrate  brain  i n the  midline  approximate l e v e l  w i t h a t r a n s e c t i o n at the approximate l e v e l  avian  bird.  which  Animals  o f L i n e B do  not  activity.  A b b r e v i a t i o n s : AHP - a r e a h y p o t h a l a m i p o s t e r i o r i s , AM - N u c l e u s a n t e r i o r m e d i a l i s h y p o t h a l a m i , A n l - N u c l e u s a n n u l a r i s , APH A r e a p a r a h i p p c a m p a l i s , BO - o l f a c t o r y b u l b , CA - a n t e r i o r commissure, Cb - c e r e b e l l u m , CCV - v e n t r a l c e r e b e l l a r commissure, CHCS - c o r t i c o h a b e n u l a r and c o r t i c o s e p t a l t r a c t , CO - o p t i c c h i a s m , CoS - s e p t a l c o m m i s s u r a l n u c l e u s , CP - p o s t e r i o r commissure, CS - c e n t r a l s u p e r i o r n u c l e u s ( B e t c h e r e w ) , CT t e c t a l commissure, DBC - d e c u s s a t i o n b r a c h i u m c o n j u n c t i v u m , DMA - d o r s o m e d i a l a n t e r i o r t h a l a m i c n u c l e u s , DMP - d o r s o m e d i a l p o s t e r i o r t h a l a m i c n u c l e u s , DSD - s u p r a o p t i c d o r s a l d e c u s s a t i o n , DSV - s u p r a o p t i c v e n t r a l d e c u s s a t i o n , EW - E d i n g e r - W e s t p h a l n u c l e u s , FD - d o r s a l f u n i c u l u s , FLM - m e d i a l l o n g i t u d i n a l f a s c i c u l u s , FV - v e n t r a l f u n i c u l u s , GC - c u n e a t e and g r a c i l e n u c l e i , GCt - c e n t r a l g r a y , HA - a c c e s s o r y h y p e r s t r i a t u m , Hb h a b e n u l a r n u c l e u s , Hp - h i p p o c a m p u s , HV - v e n t r a l h y p e r s t r i a t u m , IM - i n t e r m e d i a t e n u c l e u s , IP - i n t e r p e d u n c u l a r n u c l e u s , LFM supreme f r o n t a l l a m i n a , LH - h y p e r s t r i a t a l l a m i n a , LMD - d o r s a l m e d u l l a r y l a m i n a , LPO - p a r o l f a c t o r y l o b e , MNV - m e s e n c e p h a l i c t r i g e m i n a l n e r v e n u c l e u s , N - n e o s t r i a t u m , NC - c a u d a l n e o s t r i a t u m , N I I I - o c c u l o m o t o r nerve, nIV - t r o c h l e a r n u c l e u s , nX - m o t o r n u c l e u s v a g u s , n X I I - h y p o g l o s s a l n u c l e u s , 01 i n f e r i o r o l i v a r y n u c l e u s , OMd - d o r s a l p a r t , o c u l o m o t o r n u c l e u s , OMv - v e n t r a l p a r t , o c u l o m o t o r n u c l e u s , Ov - o v o i d n u c l e u s , P p i n e a l , PaM - p a r a m e d i a n n u c l e u s , PMH - p o s t e r i o r p a r t , m e d i a l h y p o t h a l a m i c n u c l e u s , PMI - p a r a m e d i a n i n t e r n a l t h a l a m i c n u c l e u s , POA - a n t e r i o r p r e o p t i c n u c l e u s , POM - m e d i a l p r e o p t i c n u c l e u s , PVM - p e r i v e n t r i c u l a r m a g n o c e l l u l a r n u c l e u s , Rgc g i g a n t o c e l l u l a r r e t i c u l a r n u c l e u s , RP - p o n t i n e c a u d a l r e t i c u l a r n u c l e u s , RPgc - g i g a n t o c e l l u l a r p a r t , c a u d a l p o n t i n e r e t i c u l a r n u c l e u s , Ru - r e d n u c l e u s , S - n u c l e u s s o l i t a r i u s , SCE e x t e r n a l c e l l u l a r s t r a t u m , SCI - i n t e r n a l c e l l u l a r s t r a t u m , SL l a t e r a l s e p t a l n u c l e u s , SM - m e d i a l s e p t a l n u c l e u s , TO o l f a c t o r y t u b e r c l e , TSM - s e p t o m e s e n c e p h a l i c t r a c t , TU - t u b e r a l n u c l e u s , V - v e n t r i c l e , vm - v e n t r o m e d i a l i n t e r n a l c e r e b e l l a r nucleus  244  245  Figure  36.  Bilateral  a l t e r n a t i n g walking a c t i v i t y  spontaneously  locomoting b i r d before  paralyzation.  The t r a n s e c t i o n  post-decerebration saggital muscles traces  level  spontaneous  from  left  and r i g h t  showing spontaneous  sartorius  (dotted line)  from  treadmill ITC n e r v e s  (B) which allows  left  and r i g h t  ITC  (*)  w a l k i n g . B: S u b s e q u e n t  ENG  i n the p a r a l y z e d animal  walking pattern a c t i v i t y .  * The i l i o t i b i a l i s c r a n i a l i s mammalian  (A) a n d a f t e r  l o c o m o t i o n i n shown i n t h e  s e c t i o n . A: EMG t r a c e s d u r i n g spontaneous  in a  (ITC) m u s c l e i s synonymous w i t h t h e  muscle.  246  A - PRE-PARALYZED EMG  B - PARALYZED ENG LEFT ITC  RIGHT ITC 2  247  sec  Figure  37.  stepping  Electromyographic  (LPECT)  pectoralis  m u s c l e s and r i g h t  spontaneous right  (RITC)  and  (LITC) i l i o t i b i a l i s c r a n i a l i s m u s c l e s d u r i n g a b o u t o f  s p o n t a n e o u s a c t i v i t y . The PECT m u s c l e depressor e s s e n t i a l hip  (EMGs) s h o w i n g  and f l y i n g a c t i v i t y . The EMGs were t a k e n f r o m t h e  (RPECT) and l e f t left  records  flexor  for flight  i s the major  and t h e ITC m u s c l e  i n birds.  248  wing i s t h e major  RPECT  LPECT  RITC  LITC  249  (Figure  36B)  (see  spontaneously  also  Chapter  6 ) . B o t h a n i m a l s were  a c t i v e p r i o r to paralyzation.  Five  strongly  other  s p o n t a n e o u s a n i m a l s w h i c h were s u b s e q u e n t l y p a r a l y z e d d e m o n s t r a t e any curarization stimulation Chapters  spontaneous  and to  required  initiate  x  fictive'  either electrical  Xfictive'  electrical al.,  this  stimulation  1986,  1987;  thesis)  or  to  (N=122) r e q u i r e d  of brainstem  (Sholomenko and  or  (see  Steeves,  i s displayed  1)  Steeves,  1987;  focal  (Steeves  Sholomenko, of  i n t o the  same  locomotor  1987b; Sholomenko, t h i s  (see  of t r a n s e c t i o n  of these b i r d s  Decerebration  either:  locomotor regions  antagonists  evoke l o c o m o t o r b e h a v i o u r s  10  chemical  intracerebral microinjection  agonists  approximate l e v e l of  after  locomotor patterns  Sholomenko and  2)  neurotransmitter regions  or  not  2-6).  Non-spontaneous animals  et  locomotion  did  Chapters 2-6).  averaged  The  f r o m a random  i n Figure  35  thesis)  (line  sample  B).  Level  Spontaneous  The  transection  extended  from the  dorsally  to the  ventrally. in  This  addition  Transections  level  i n s i x of the  caudal border of the  r o s t r a l border of the transection  to portions  eliminated  of the  which e l i m i n a t e d  spontaneous  habenular  nucleus  anterior preoptic the  anterodorsal  entire  nucleus  telencephalon  thalamus  more d o r s o c a u d a l  250  birds  (DMA).  structures  (N=2),  i n c l u d i n g the p o s t e r i o r extended to  dorsally  from  a n t e r i o r to the  internal  stratum.  One  of these b i r d s ,  separated the e n t i r e  thalamus,  the brainstem,  response  elicited  to treadmill  belt  nigra  (nucleus of the  (TPc), the  of the hypothalamic (LHA)  hypothalamic  with  a  nucleus  stepping i n  stimulation.  lenticularis  s p i r i f o r m nucleus  nuclei areas]  the  posterior  prolonged hindlimb  ansa  lateral  caudal  hypothalamic  I n a l l o f t h e above s p o n t a n e o u s a n i m a l s , nucleus  (CP)  Two  and p o r t i o n s o f  commissure and p a r t o f t h e m e d i a l p o s t e r i o r from  commissure  t r a n s e c t i o n s w h i c h a b l a t e d more  cellular  transection that  ovoid nucleus,  caudal to the p o s t e r i o r  i n c l u d i n g t h e e x t e r n a l (SCE)  (SCI)  and  a n t e r i o r p r e o p t i c nucleus v e n t r a l l y .  spontaneous b i r d s had structures  thalamic nuclei  [e.g. p o s t e r i o r remained  the  subthalamic  (nAL)), the s u b s t a n t i a and  caudal portions  (AHP)  and  lateral  intact.  Non-spontaneous  Neuroanatomic a n a l y s i s Canada g e e s e ,  1 P e k i n duck)  spontaneous locomotion demonstrated  that  transection  levels  animals, the  chosen  from t h o s e which d i d not  after  the m a j o r i t y of animals than those  S p l , but  left  found  removed t h e  the bulk of the p o s t e r i o r  (9  elicit  h a d more c a u d a l  i n spontaneous b i r d s .  the bulk of the nucleus  completely  a t random  t h e d e c e r e b r a t i o n ( F i g . 35B)  t h e t r a n s e c t i o n e l i m i n a t e d t h e most r o s t r a l  transections and  of the ten b i r d s  and  251  intact.  subthalamic  lateral  In  two  portions of  These  nucleus  hypothalamic  (nAL) nuclei.  Also,  transection  rostral  region  Slightly locomotion  l e v e l s i n three animals  of the substantia more r o s t r a l  in 4 birds.  damaged t h e most  nigra.  lesions also  In t h e s e animal,  eliminated  spontaneous  the substantia  S p l n u c l e i were s p a r e d , b u t a g a i n t h e nAL and l a t e r a l p o s t e r i o r hypothalamic  n u c l e i were  One b i r d w h i c h d i d n o t p e r f o r m decerebration those All  seen  had a t r a n s e c t i o n  spontaneously  i n animals which e x h i b i t e d  spontaneous  possible  that  r a p i d l y than  the condition  after  t h i s animal  be d e t e r m i n e d ,  of the preparation  i n the other b i r d s .  252  as  locomotion.  i n t h e spontaneous  l o c o m o t i o n cannot  and  o f t h e same l e v e l  spontaneous  a l s o p r e s e n t i n t h i s a n i m a l . R e a s o n s why elicit  and  excised.  w h i c h was  o f t h e n u c l e i which remained  nigra  birds  were  d i d not but i t i s  deteriorated  more  DISCUSSION  The  results  in  mammals,  of  the  acute  from t h i s  preservation  caudal  the  spontaneity  locomotor  chemical  stimulation  Steeves, The  between ansa  the  the  Sholomenko,  areas part  of  the  mammalian  subthalamic  et  been  al.,  within  the  Reiner  wedge  non-spontaneous the  most  outflow spared  of in  the both  Several account  for  of but  rostral  nucleus  et  the  the  the  avian  basal  rostral  in  Spl,  have  precollicular-premammillary  to  and/or  of  tissue  nucleus and  (TPc).  of  portion  The n A L ,  comparable  al.,  1978),  spontaneous receives  (Reiner  et  al.,  forth  in  the  posterior  is  in  lying  based  to  the  while  nigra  of  the  (Brauth lie  the birds. the  A l l  but  major 1984),  was  lesions.  been  levels  the  (Sholomenko  rostral  removed  which  ganglia  in  T h e L H A a n d PHA a l s o  the  and c a u d a l  different  wedge  most  nigra  w h i c h was  of  regions  lateral  (Brauth et  preserved  portion  electrical  included the  1984).  tissue  boundaries  ability  mammalian s u b s t a n t i a  al.,  explanations the  in  considerations,  compared to  1978;  of  substantia  on h o d o l o g i c a l  has  levels  as  thesis).  ( L H A & PHA) a n d t h e  primarily  TPc  present  the  locomotion  the  locomotor  this  nuclei  to  birds,  transections  alter  response  in  within  caudal  not  brainstem  (nAL),  lying  that  spontaneous  More do  in  transection  lenticularis  compact  region  but  w h i c h were  two  hypothalamic  of  demonstrate  allows  rhythms  1987;  nuclei  a  preparation.  generate  and  of  diencephalon  decerebrate  eliminate  study  of  versus  253  put  activity  an  attempt  to  in  precollicular-postmammillary  t r a n s e c t e d mammals. W e t z e l and S t u a r t s t r u c t u r e s remaining  (1976) suggest t h a t t h e  i n t h e p r e c o l l i c u l a r - p r e m a m m i l l a r y but  removed from t h e p r e c o l l i c u l a r - p o s t m a m m i l l a r y p r e p a r a t i o n , c o n s i s t i n g o f the p o s t e r i o r hypothalamic,  subthalamic  and  v e n t r a l p o s t e r i o r t h a l a m i c neurons, i n c r e a s e t h e g e n e r a l e x c i t a b i l i t y o f more c a u d a l neurons. S i m i l a r l y , Armstrong, i n a recent review preserved  (1986), p o s t u l a t e d t h a t c e l l s c o n t a i n e d w i t h i n t h e  s l i c e o f t i s s u e , p o s s i b l y a r i s i n g from t h e p o s t e r i o r  hypothalamus, zona i n c e r t a o r H a t o n i c (as opposed t o r h y t h m i c  and H  2  f i e l d s of Forel,  or patterned)  provide  e x c i t a t o r y input  t o downstream motor r e l a t e d s t r u c t u r e s . G a r c i a - R i l l and S k i n n e r (1986),  on t h e o t h e r hand, suggested t h a t t o n i c GABAergic  subthalamic  n u c l e u s p r o j e c t i o n s t o t h e s u b s t a n t i a n i g r a (SN),  which a r e spared a f t e r t h e p r e c o l l i c u l a r - p r e m a m m i l l a r y t r a n s e c t i o n , i n h i b i t an i n h i b i t o r y GABAergic p r o j e c t i o n from t h e SN t o t h e p e d u n c u l o p o n t i n e n u c l e u s  (mesencephalic locomotor  r e g i o n ) . Thus, locomotor p a t t e r n s a r e e f f e c t i v e l y ( r e l e a s e d ) and can express  disinhibited  themselves i n t h e acute premammillary  cat preparation. Their hypothesis  accounts f o r t h e l o s s o f  spontaneous a c t i v i t y a f t e r a more c a u d a l t r a n s e c t i o n t h r o u g h t h e e l i m i n a t i o n o f t h e i n h i b i t i o n from t h e SN t o t h e PPN. T h i s theory i s supported  by t h e f i n d i n g t h a t i n j e c t i o n o f GABA  a n t a g o n i s t s i n t o t h e SN b l o c k s spontaneous s t e p p i n g i n t h e premammillary p r e p a r a t i o n and t h a t s t e p p i n g can be r e i n s t a t e d by i n j e c t i o n o f GABA o r muscimol i n t o t h e SN ( G a r c i a - R i l l and Skinner,  1986). However, s p e c i f i c damage t o t h e s u b t h a l a m i c  n u c l e u s , which s h o u l d , a c c o r d i n g t o G a r c i a - R i l l and. S k i n n e r  254  (1986),  through  locomotion, or chorea  disinhibition  o n l y r e l e a s e s motor b e h a v i o u r s  diencephalic region, defined  as t h e s u b t h a l a m i c  locomotor  region  l o c o m o t i o n when e l e c t r i c a l l y i n locomotor  subthalamic  such  inhibit  as h e m i b a l l i s m u s  nucleus  Brudzynski  electrophysiological^  (SLR), w i l l  elicit  stimulated. It i s intimately  control  and l i e s  dorsomedially to the  (Shik and O r l o v s k y ,  1 9 7 6 ) . Mogenson a n d c o - w o r k e r s 1985;  pathway,  (Hammond e t a l . , 1 9 7 9 ) .  Another  involved  o f an i n h i b i t o r y  1976; O r l o v s k y a n d S h i k ,  (Mogenson,  et al., 1988) u s e d  1984; Mogenson e t a l . ,  a variety  of neuroanatomical  tracing  t e c h n i q u e s t o d e s c r i b e t h e SLR a s l y i n g w i t h i n t h e zona  incerta  (ZI) a n d l a t e r a l  This  hypothalamic  r e g i o n has been found t o p r o j e c t  cuneiform strongly  and r e t i c u l a r implicated  i n motor c o n t r o l  Garcia-Rill  corroborates that  and S k i n n e r ,  (Swanson et al., 1984;  1986). T h e i r (1969),  t h e SLR b o t h t o t h e MLR and r e t i c u l a r  that  t h e SLR-evoked l o c o m o t i o n  axons o f p a s s a g e b u t from  results  stimulation  comes f r o m  the finding that  picrotoxin  i n t o t h e SLR i n d u c e d  precollicular-premammillary  infusion  d i r e c t e d behaviour  who  used projections  formation.  n o t from  Evidence  stimulation of  o f neuronal  receptors  o f t h e GABAergic a n t a g o n i s t  locomotion  cat (Eldridge  i s the hypothesis that  and Jordan,  evidence  techniques to describe d i r e c t  from  interest  which themselves a r e  1970a,b; S t e e v e s  found by O r l o v s k y  electrophysiological  (LHA) i n t h e r a t .  t o the pedunculopontine,  formation nuclei,  Mogenson e t a l . , 1985; O r l o v s k y , 1984;  area  i n the e t a l . , 1985). Of  t h e SLR r e g i o n u n d e r l i e s g o a l  ( S h i k a n d O r l o v s k y , . 1976; Mogenson, 1984;  255  Mogenson e t al., limbic 1985/ the  system  influences  subthalamic  animal  nucleus)  i s a possible  those  found  primativum)  and l a t e r a l  Garcia-Rill that  i n mammals. The nAL  decerebrate  (subthalamic  1984), p a l l i d u m ( p a l e o s t r i a t u m ( B r a u t h e t al.,  suggested  and S k i n n e r ,  i n birds  1978).  pathway i s e q u i v a l e n t t o  i n mammals  al.,  (McGeer e t  1986), b u t i t i s i n t e r e s t i n g t o  t h e s t r u c t u r e s t o w h i c h nAL p r o j e c t  motor-related unclear,  i n the high  s p i r i f o r m nucleus  the GABAergic p r o j e c t i o n  note  o f t h e spontaneous  animals.  conserved  i s p r e s e n t l y unknown w h e t h e r t h i s  1984;  al.,  (Mogenson e t  projects t o the avian equivalent of the substantia  (TPc) ( R e i n e r e t al.,  nigra  source  i n high decerebrate  the structures  parallel  behaviours  which t h e  1 9 8 8 ) . Thus, t h e SLR, i n a d d i t i o n t o  nucleus  activity  In b i r d s ,  locomotor  e t al.,  Brudzynski  locomotor  It  1985) a n d may be t h e l o c u s t h r o u g h  ( R e i n e r e t al.,  are a l l  1984). I t remains  however, w h e t h e r t h e nAL i s t h e n e u r a l s u b s t r a t e  responsible  f o r spontaneous locomotion  i n high  decerebrate  birds. The  afferent  and e f f e r e n t  projections  o f the hypothalamic  n u c l e i which a r e p r e s e r v e d i n t h e h i g h decerebrate  spontaneous  preparation  i n birds,  (LHA a n d PHA) have n o t b e e n e l u c i d a t e d  a l t h o u g h B e r k a n d Hawkin pigeon,  (1985) make b r i e f m e n t i o n t h a t i n  a s i n r a t (Mogenson e t al.,  region projects to the l a t e r a l no  1985), t h e  hypothalamic  parahippocampal  a r e a . Thus,  although  a v i a n e q u i v a l e n t o f t h e SLR/zona i n c e r t a h a s y e t b e e n  recognized  i n birds  homology a p p e a r s  ( K a r t e n a n d Hodos,  to exist  1967; Zweers,  between l i m b i c  256  1971), some  t o hypothalamic  c o n n e c t i o n s i n b i r d s and mammals (Berk and F i n k e l s t e i n , 1983) which may u n d e r l i e t h e p r e s e r v a t i o n o f spontaneous l o c o m o t i o n a f t e r a r o s t r a l d e c e r e b r a t i o n . I n b i r d s , as i n mammals, more i n f o r m a t i o n i s r e q u i r e d t o determine which n u c l e u s o r combination o f n u c l e i i n the conserved d i e n c e p h a l i c t i s s u e i s e s s e n t i a l f o r spontaneous l o c o m o t i o n . Furthermore,  the exact  r o l e of t h i s region, although p o s s i b l y limbic-motor r e l a t e d , remains t o be determined. The l a c k o f i n f o r m a t i o n r e g a r d i n g t h e a v i a n pathways which l e a d t o spontaneous l o c o m o t i o n a f t e r a r o s t r a l t r a n s e c t i o n o f t h e n e u r a x i s make i t i m p o s s i b l e t o d e l i n e a t e t h e n e u r a l s u b s t r a t e f o r t h e a c t i v i t y a t t h i s time  (Armstrong,  However, t a k e n t o g e t h e r w i t h our p r e v i o u s r e s u l t s  198 6 ) . demonstrating  t h a t b i r d s p o s s e s s locomotor c i r c u i t r y which i s v e r y s i m i l a r t o t h a t o f mammals, we h y p o t h e s i z e t h a t t h e n e u r a l s u b s t r a t e and mechanisms i n v o l v e d i n a v i a n h i g h d e c e r e b r a t e spontaneous l o c o m o t i o n w i l l be t h e same as t h o s e found i n t h e mammalian preparation.  257  CHAPTER 8 SUMMARY DISCUSSION  258  In t h i s multimodal  t h e s i s , I have a t t e m p t e d t o t a k e an  approach to the  study of avian  m o t o r c o n t r o l mechanisms. T h i s selective  vertebrates.  i n j e c t i o n studies Results  electrophysiology,  stimulation  from a v i a n  and  vertebrate  immunohistochemistry  control My cord The  the  was  studies  included  examine two  to  1960,  the  aspects  corroborate  lumbosacral  (ten Cate,  cord,  the  spinal cord  1962). T h i s  geese demonstrated the has  a rhythmic pattern (Sholomenko and  generators i n the  Steeves,  found i n v i r t u a l l y  and  receptor  i n an  attempt  to  in  further  locomotor  below, t h e  oscillators  brainstem  information  1976;  low  thoracic  spinal  in birds.  could  ^spinal  r e s u l t was  s u p p o r t e d by  of the  ability  (LPG)  elicit  to  N  low  stepping' the  thoracic  finding spinal  s p i n a l s t e p ' '. T h i s  presence of that  an  are  spinal  capable of  cord producing  influences  1 9 8 7 ) . S i m i l a r s p i n a l LPGs have b e e n  1981;  examined, p o s s i b l y Graham-Brown,  Eidelberg, are  1 9 8 1 ) . As  m o d u l a t e d b o t h by  (Kuypers,  (Grillner,  of  absence o f descending  ( E i d e l b e r g e t al., Stuart,  use  pigeons with  a l l vertebrates  W e t z e l and  from the  other  finding that  been a t t r i b u t e d t o the  locomotor p a t t e r n  primates  brainstem  from  o f motor f u n c t i o n  f o l l o w i n g complete t r a n s e c t i o n  stepping  and  neuroanatomy,  n e u r o a n a t o m i c a l pathways i n v o l v e d  previous  first  that  system  in birds.  lesions to  isolated  or  r e s u l t s from  i n b i r d s with those  a u t o r a d i o g r a p h y have b e e n i n c o r p o r a t e d characterize  c e n t r a l nervous  a p p r o a c h compares my  l e s i o n , brainstem e l e c t r i c a l  neurochemical  integrated  1985;  1982)  and  McClellan,  259  by  1911,  will  be  pathways  afferent  1986).  excluding 1914; discussed descending  peripheral  t The  second  a s p e c t o f my  s t u d y was  to determine  b r a i n s t e m d e s c e n d i n g pathways which impinge responsible rhythmic  f o r the  locomotor  low t h o r a c i c  voluntary  locomotor studied  Shik,  Eidelberg  Armstrong, injection provided  1986).  e t al.,  ( C h a p t e r s 2-5)  i n locomotor  1987).  formation  nucleus  (RP)  (mMRF). Two  substantially  formation  nuclei  1987).  This  same as t h a t  found  Steeves  role  for a l l  1968a,b; O r l o v s k y and  and  Jordan,  and  1984;  neurochemical and  have  incomplete, of the  reticular  four avian brainstem r e t i c u l a r  1986;  Effective  elicited  by  reticular  electrical  Sholomenko and  Steeves,  (Cnd)  and v e n t r a l  nuclei,  o f t h e s e r e g i o n s , Cnd  and  reticulospinal  only sparsely to the s p i n a l  260  be  (Cnv)  the v e n t r a l  and t h e m e d i a l m e s e n c e p h a l i c  t o the descending  formation  1987;  locomotion-inducing stimulation  and mMRF, s t r u c t u r e s w h i c h w i l l  project  essential  Steeves,  stimulation  were l o c a l i z e d t o t h e d o r s a l  reticular  the  control.  of the c e n t r a l medullary  RP  1981;  important  ( S t e e v e s e t al.,  e t al.,  that  pathways a r e n e c e s s a r y f o r  f r o m w h i c h l o c o m o t i o n c a n be  stimulation  sites  of the avian  although n e c e s s a r i l y  I have i d e n t i f i e d  Steeves  lesions  s t u d i e s were t h e n u n d e r t a k e n  information r e g a r d i n g the  regions  Selective  (Lawrence and K u y p e r s ,  Electrical  additional,  formation  of the  p a t t e r n s , i s the  vertebrates 1976;  control  Sholomenko and  the r e t i c u l o s p i n a l  are  ongoing  c o r d demonstrated  1986;  major  on t h e LPGs and  from t h e b r a i n s t e m r e t i c u l a r  ( S t e e v e s e t al., that  and  oscillations.  spinal  pathways a r i s e  finding,  initiation  the  parts  pontine  reticular  Cnv,  contribute  pathways,  while  discussed subsequently,  cord  (Cabot  e t al.,  1982;  Webster and S t e e v e s , The  view that  1988).  n e u r o n s i n Cnd a n d Cnv g i v e r i s e  common b r a i n s t e m - s p i n a l l o c o m o t o r of evidence First,  other than  lesion  to the f i n a l  pathway i s s u p p o r t e d by l i n e s  and e l e c t r i c a l  stimulation  Cnd a n d Cnv n e u r o n s r e t r o g r a d e l y l a b e l l e d  from t h e s p i n a l  c o r d have b e e n c o - l o c a l i z e d w i t h l o c o m o t i o n - i n d u c i n g sites  i n t h e same b i r d  neuroanatomical  results  brainstem n u c l e i Cnd  ( S t e e v e s e t al., 1 9 8 7 ) . demonstrate  stimulation  Second,  t h a t many l o c o m o t i o n - r e l a t e d  s e n d p r o j e c t i o n s t o Cnd a n d Cnv, t h u s  a n d Cnv i n an i d e a l p o s i t i o n  data.  to integrate  placing  and p r o j e c t  motor  i n f o r m a t i o n t o t h e c o r d . The m o t o r r e l a t e d n u c l e i p r o j e c t i n g t o Cnd/Cnv, many o f w h i c h have b e e n  identified  electrophysiologically,  i n c l u d e t h e RP, mMRF,  (Rgc)  (Rpc) r e t i c u l a r  and p a r v o c e l l u l a r  descending  tract  intercollicularis  and n u c l e u s  region  (ICo), tectum,  cerebellum, Area v e n t r a l i s magnus  1984;  A r e n d s a n d Dubbeldam,  1984;  W i l d e t a l . , 1985; R e i n e r  direct  (Webster,  intracerebral  formation,  (TTD),  r e d nucleus  intermedium, and n u c l e u s  1984; Hunt a n d K u n z l e , and K a r t e n ,  neurochemical  or block locomotion  were e f f e c t i v e include  1982).  microinjection  (Cnv o n l y ) The  (Chapters  at e l i c i t i n g  cholinergic  al.,  p e r s o n a l communication; Arends e t  neurotransmitter agonists/antagonists into these elicit  trigeminal  nucleus  archistriatum  of Tsai,  raphe  gigantocellular  of specific r e g i o n s can  from  these  which  regions  (Cnd & C n v ) , G A B A e r g i c a n t a g o n i s t s  and g l u t a m a t e r g i c a g o n i s t s  studies u t i l i z i n g  Finally,  3-5). Neurochemicals  locomotion  agonists  1976; W i l d ,  (Cnd a n d C n v ) .  neurochemical  261  i n j e c t i o n were  combined  w i t h a v a i l a b l e anatomical, immunohistochemical and r e c e p t o r a u t o r a d i o g r a p h i c data from the l i t e r a t u r e i n an attempt t o differentiate afferents  t o Cnd and Cnv which e x c i t e or i n h i b i t  these n u c l e i . My a n a l y s i s  revealed  motor r e l a t e d c h o l i n e r g i c input  s e v e r a l p o t e n t i a l sources o f  t o Cnd and Cnv. P o s s i b l e  c h o l i n e r g i c a f f e r e n t s t o Cnd a r i s e from the s u b t r i g e m i n a l nucleus, TTD, RP, l a t e r o d o r s a l tegmental nucleus, and nucleus isthmi, TTD,  pars p a r v o c e l l u l a r i s , w h i l e those t o Cnv may a r i s e from  Rpc, Rgc and the nucleus mesencephalicus, pars profundus.  In a d d i t i o n ,  both Cnd and Cnv c o n t a i n  neurons. While i t i s p o s s i b l e formation  that  intrinsic  cholinergic  TTD and other r e t i c u l a r  (e.g. RP, Rgc, Rpc) s t r u c t u r e s  g i v e r i s e t o the  c h o l i n e r g i c motor connection, as e l e c t r i c a l s t i m u l a t i o n r e g i o n s g i v e s r i s e t o locomotion, i n s u f f i c i e n t  o f these  information i s  a v a i l a b l e t o u n e q u i v o c a l l y i d e n t i f y any s i n g l e pathway, or combination o f pathways, as b e i n g r e s p o n s i b l e  f o r my r e s u l t s . I t  i s c l e a r , however, from the e f f e c t s o f c a r b a c h o l on locomotion and  the a b i l i t y o f a t r o p i n e ,  a muscarinic antagonist, t o block  the  locomotor e f f e c t s e l i c i t e d by c a r b a c h o l , t h a t neurons i n  both Cnd and Cnv appear t o be under c h o l i n e r g i c c o n t r o l v i a muscarinic  receptors.  While c h o l i n e r g i c a g o n i s t i n j e c t i o n e l i c i t s  locomotion i n  both Cnv and Cnd, GABAergic a n t a g o n i s t s induce locomotion only when i n j e c t e d i n t o Cnv. E q u a l l y , locomotion only when i n f u s e d  i n t o Cnv. I t i s l i k e l y ,  t h a t neurons i n Cnd and Cnv p l a y locomotor c o n t r o l ,  GABA i n j e c t i o n b l o c k s  s l i g h t l y different roles i n  r e c e i v i n g and i n t e g r a t i n g input  262  therefore,  from  different  parts  inputs t o these different  o f theneuraxis. nuclei  (described,  cytoarchitecture  suggest t h a t t h i s  agonist  neuroanatomical  above) a n d t h e i r  a n d Hodos,  i s t h e case.  1967) w o u l d  , through the i n f u s i o n o f the  NMDA i n t o b o t h Cnd a n d Cnv i n t h e a v i a n  p r e p a r a t i o n . While glutamatergic be  i npart,  (Karten  Locomotion i s a l s o e l i c i t e d glutamatergic  The d i f f e r e n t  input t o both n u c l e i remains t o  c h a r a c t e r i z e d i nb i r d s , i n other  species,  reticulospinal  n e u r o n s have b e e n d e m o n s t r a t e d t o r e c e i v e g l u t a m a t e r g i c from s e v e r a l s o u r c e s . excitatory  I n lamprey,  intrinsic  reticular  amino a c i d - c o n t a i n i n g i n t e r n e u r o n s ,  c o n t a i n NMDA r e c e p t o r s , trigeminal,  have b e e n r e p o r t e d  v e s t i b u l a r and a s c e n d i n g  neurotransmitters undetermined  utilized  which  input formation  themselves  t o receive  spinobulbar  i n p u t . The  by t h e l a t t e r pathways a r e  (Dubuc e t a l . , 1 9 8 8 ) . However, t h e i n t e r n e u r o n s  h a v e b e e n d e m o n s t r a t e d t o i m p i n g e on r e t i c u l o s p i n a l  neurons  (Dubuc e t a l . , 1 9 8 8 ) . I n mammals, d e s c e n d i n g e x c i t a t o r y amino acidergic  (EAA) i n p u t  to this  s t r u c t u r e s has been r e p o r t e d mammals, n e u r o c h e m i c a l shown t o be e f f e c t i v e the al.,  reticular  from t e l e n c e p h a l i c  (Fagg a n d F o s t e r ,  stimulation using at e l i c i t i n g  formation  locomotion  (Garcia-Rill  neuronal variety  when i n f u s e d i n t o  and Skinner,  1987a; Noga e t  i s no i n f o r m a t i o n  p a t h w a y s o r e x c i t a t o r y amino a c i d - c o n t a i n i n g  e l e m e n t s . However, c o m b i n e d w i t h o f s t u d i e s , my r e s u l t s  f o r glutamate  1983). A l s o i n  g l u t a m a t e has been  1 9 8 8 ) . I n b i r d s , t o my knowledge, t h e r e  about g l u t a m a t e r g i c  role  region  suggest  t h e above d a t a  an i m p o r t a n t  excitatory  in. t h e c o n t r o l o f l o c o m o t i o n - r e l a t e d  263  from a  reticular The those  formation  structures.  above f i n d i n g s  found  (Grillner  f o r C n d a n d Cnv,  f o r synonymous s t r u c t u r e s  i n other  similar to  vertebrates  Armstrong,  1986),  suggest t h a t r e t i c u l o s p i n a l  n e u r o n s i n C n d a n d Cnv s e r v e  as the  brainstem  cord  , 1976;  which are  LPGs. The h i g h e r  l e v e l s o f c o n t r o l , the  w h i c h i m p i n g e on a n d m o d u l a t e t h e have n o t b e e n c h a r a c t e r i z e d regions and  Two  and  rostral  reticular  sparsely  communication;  to spinal  structures  formation  same e x t e n t .  nuclei,  However,  several  c o n t r o l o v e r Cnd  2-7).  candidates.  only  input  t o the  neural  have b e e n i d e n t i f i e d w h i c h may e x e r t  Cnv ( C h a p t e r s  likely  reticular  liaison  formation  n u c l e i , RP a n d mMRF a r e  B o t h RP a n d mMRF p r o j e c t m a i n l y t o Cnd, Cnv t o the  s p i n a l cord  Webster and Steeves,  (Webster,  personal  1 9 8 8 ) . RP r e c e i v e s  afferent  f r o m s e v e r a l m o t o r r e l a t e d s o u r c e s i n c l u d i n g TTD,  tectum,  c e r e b e l l u m , v e s t i b u l a r n u c l e i a n d Cnd/Cnv. From a neuroanatomical integrate  standpoint,  therefore,  a broad range o f sensory  RP i s i d e a l l y  information  downstream motor s t r u c t u r e s . E v i d e n c e t h a t role  which demonstrate t h a t  locomotion i n b i r d s be  and i n f l u e n c e  this  region  i n l o c o m o t o r c o n t r o l comes f r o m e l e c t r i c a l  studies  evoked by t h e  1-5).  Furthermore,  i t i s not yet  on RP, t h e d a t a  (see  Chapters  264  elicits  locomotion can and the i n t o RP  p o s s i b l e t o determine t h e  pathways t h r o u g h which t h e s e n e u r o t r a n s m i t t e r s effects  stimulation  NMDA, b u t n o t c h o l i n e r g i c a g o n i s t s ,  While  has a  stimulation  i n j e c t i o n o f GABAergic a n t a g o n i s t s  glutamate agonist ( C h a p t e r s 4,5).  (Chapters  RP e l e c t r i c a l  situated to  exert  their  1-5) s u g g e s t t h a t  RP, l i k e  s e v e r a l o t h e r l o c o m o t o r - r e l a t e d s t r u c t u r e s , appears t o e l i c i t locomotor b e h a v i o u r m a i n l y t h r o u g h i t s p r o j e c t i o n s t o Cnd and Cnv.  The n e u r o t r a n s m i t t e r s which subserve t h e c o n t r o l a l s o  remain t o be determined, a l t h o u g h , from t h e Cnd/Cnv d a t a above, a c e t y l c h o l i n e and glutamate are p o s s i b l e c a n d i d a t e s . S i m i l a r t o RP, t h e mMRF p r o j e c t s m a i n l y t o t h e b r a i n s t e m r e t i c u l a r f o r m a t i o n n u c l e i and o n l y s p a r s e l y t o t h e s p i n a l c o r d . The mMRF has s t r o n g r e c i p r o c a l c o n n e c t i o n s w i t h t h e deep t e c t a l layers  ( i n t e r c o l l i c u l a r n u c l e u s , ICo) which appear t o form one  l i n k o f t h e a v i a n b a s a l g a n g l i a l o o p (Chapter 2 ) . E l e c t r i c a l s t i m u l a t i o n o f t h e mMRF e l i c i t s l o c o m o t i o n i n b i r d s  (Chapter 2 ) .  In a d d i t i o n , n e u r o c h e m i c a l i n j e c t i o n s t u d i e s (Chapters 4,5) demonstrate  t h a t t h e e l e c t r i c a l t h r e s h o l d f o r l o c o m o t i o n can be  reduced by t h e i n f u s i o n o f p i c r o t o x i n and NMDA i n t o t h i s r e g i o n . Based on t h e above c o n s i d e r a t i o n s and those from mammalian studies 1986/  ( G a r c i a - R i l l e t a l . , 1985/  Mogenson and B r u d z y n s k i ,  see Chapter 5 ) , i t appears p o s s i b l e t h a t t h e mMRF may form  one component o f an a v i a n e q u i v a l e n t t o t h e mammalian m e d i a l MLR.  A second component, p o t e n t i a l l y e q u i v a l e n t t o t h e mammalian  l a t e r a l MLR, i s found i n t h e r e g i o n o f t h e m i d b r a i n i n t e r c o l l i c u l a r nucleus  (ICo).  ICo r e c e i v e s i n p u t from t h e s p i n a l c o r d (Hunt and K u n z l e , 1976/  Webster and Steeves, i n p r e p a r a t i o n ) , deep t e c t a l  and cuneate and g r a c i l e n u c l e i to  TTD,  1982/  layers,  ( W i l d e t a l . , 1987). I t p r o j e c t s  Rgc, Cnv and h i g h c e r v i c a l c o r d (Reiner and K a r t e n ,  Webster and Steeves, i n p r e p a r a t i o n ) . E l e c t r i c a l  s t i m u l a t i o n o f t h i s r e g i o n (Chapter 2) e l i c i t s l o c o m o t i o n i n  265  birds.  I t s c o n n e c t i v i t y suggests  t o t h e mammalian c u n e i f o r m  this  nucleus  nucleus  (Cabot  r e g i o n which has been i m p l i c a t e d through studies  as t h e l a t e r a l  1 9 8 8 ) . The mammalian control  (Steeves  Further evidence  lateral  MLR  i s believed to exert  locomotor  1983). While t h e s e  and J o r d a n ,  behaviour  ICo w i t h t h e mammalian MLR  (Chapter  study  are i n d i c a t i v e  any f i r m  equivalency  required to establish  the next  level  transection preparations activity  correlation  o f t h e a v i a n MLRs  i s to describe the n u c l e i at the a c t i v i t y of  diencephalon  nuclei  spontaneous locomotor  ( f o r review,  are implicated i n  see Armstrong,  after  activity  selective  i n decerebrate  1 9 8 6 ) . The s p o n t a n e o u s  more c a u d a l  locomotion-related  determine whether such  regions exist  i n birds, of the neuraxis  7 ) . R o s t r a l d e c e r e b r a t i o n s which p r e s e r v e d  266  nuclei  nuclei.  d e c e r e b r a t i o n s were p e r f o r m e d a t v a r y i n g l e v e l s (Chapter  et a l . ,  i s a t t r i b u t e d t o t h e c o n t r o l which t h e p r e s e r v e d  over To  picrotoxin  c a n be e s t a b l i s h e d . P a r t o f  as p r e s e r v a t i o n o f t h e s e  allows  as s e e n i n  r e g i o n s . T r a n s e c t i o n s t u d i e s have shown t h a t  i n t h e mammalian c a u d a l  control,  arises  further testing i s  o f t h e h i e r a r c h y which c o n t r o l  the mesencephalic nuclei  of a  equivalency  w i t h t h e i r mammalian c o u n t e r p a r t s  exert  r e g i o n which,  4; G a r c i a - R i l l  b e t w e e n t h e mammalian a n d a v i a n MLRs, required before  motor  1984; Noga e t a l . , 1 9 8 8 ) .  infusions into this  results  al.,  reticular  demonstrates t h a t t h e GABAergic a n t a g o n i s t  elicits  such  electrical stimulation  ( S h i k e t a l . , 1967; Noga e t  correlating  from n e u r o c h e m i c a l  the  e t a l . , 1982), a  e f f e c t s v i a p r o j e c t i o n s t o the medullary  formation  cats,  MLR  may be e q u i v a l e n t  a wedge o f  neural t i s s u e containing the subthalamic nucleus  (nucleus o f t h e  ansa l e n t i c u l a r i s ) , t h e l a t e r a l and p o s t e r i o r h y p o t h a l a m i c n u c l e i and t h e most r o s t r a l p o r t i o n o f t h e s u b s t a n t i a n i g r a y i e l d e d spontaneous  locomotion i n b i r d s . A b l a t i o n of t h i s region  r e s u l t e d i n b i r d s which- would locomote o n l y w i t h e l e c t r i c a l o r n e u r o c h e m i c a l b r a i n s t e m s t i m u l a t i o n . P r e v i o u s s t u d i e s i n mammals have demonstrated t h a t s i m i l a r d i e n c e p h a l i c s t r u c t u r e s (e.g. s u b t h a l a m i c n u c l e u s , s u b t h a l a m i c locomotor r e g i o n (SLR), zona i n c e r t a and l a t e r a l h y p o t h a l a m i c area) a r e p r e s e r v e d i n spontaneous  d e c e r e b r a t e (acute premammillary  preparation) animals (Waller et a l . ,  precollicular  1940). A l s o i n mammals,  t h e s e s t r u c t u r e s appear t o send p r o j e c t i o n s t o t h e more c a u d a l locomotor r e g i o n s ( f o r r e v i e w see Chapter 1 ) . My r e s u l t s , t h e r e f o r e , suggest t h a t c o u n t e r p a r t s o f t h e s e  mammalian  d i e n c e p h a l i c r e g i o n s a r e a l s o found i n b i r d s . Whether t h e y s e r v e as t h e l o c u s t h r o u g h which t h e a v i a n l i m b i c system governs g o a l d i r e c t e d locomotor b e h a v i o u r s , as has been suggested f o r mammals (Mogenson e t a l . ,  1985), a w a i t s f u r t h e r i n f o r m a t i o n .  My s t u d i e s have r e v e a l e d a n o v e l locomotor r e g i o n i n b i r d s which l i e s w i t h i n t h e c o n f i n e s o f t h e p o n t i n e and r o s t r a l medullary medial l o n g i t u d i n a l f a s c i c u l u s  (MLF) (Chapter 2 ) .  E l e c t r i c a l stimulation of t h i s region repeatably e l i c i t s locomotor p a t t e r n s . Furthermore, t h e l o c o m o t i o n can be r e p e a t a b l y evoked by n e u r o c h e m i c a l i n f u s i o n  ( c a r b a c h o l and  NMDA), p r o v i d i n g c o n c l u s i v e e v i d e n c e t h a t n e u r o t r a n s m i t t e r receptors  (not en p a s s a n t f i b r e s ) were s t i m u l a t e d t o produce  this effect  (Goodchild et a l . ,  1982). S e r o t o n i n e r g i c c e l l  267  b o d i e s , which s t a i n p o s i t i v e l y f o r a c e t y l c h o l i n e s t e r a s e and P a r e n t , 1981; Taccogna e t a l . ,  (Dube  i n p r e p a r a t i o n ) and l i e i n  c l o s e p r o x i m i t y t o t h e i n j e c t i o n s i t e have been i m p l i c a t e d i n t h e locomotor response. These c e l l s have been shown t o p r o j e c t t o t h e r e g i o n o f t h e m i d b r a i n p r e t e c t a l n u c l e u s near s i t e s which l o c o m o t i o n can be e l i c i t e d  from  (Dube and P a r e n t , 1981). The  r o l e o f t h e s e c e l l s i n locomotor c o n t r o l and t h e n e u r o a n a t o m i c a l s u b s t r a t e t h r o u g h which t h e c o n t r o l may be e x e r t e d , however, has y e t t o be d e t e r m i n e d . Sensory i n f o r m a t i o n a l s o appears t o have a r o l e i n motor c o n t r o l . A t l e a s t one l o c u s f o r t h e i n t e g r a t i o n o f t h i s sensory i n f o r m a t i o n may l i e w i t h i n t h e t r i g e m i n a l d e s c e n d i n g t r a c t and nucleus  (TTD), a r e g i o n which r e c e i v e s a v a r i e t y o f s e n s o r y , as  w e l l as c e n t r a l a f f e r e n t s and which, i n t u r n , p r o j e c t s t o t h e hindbrain r e t i c u l a r formation n u c l e i  (Cnd & Cnv) (see Chapters  1, 3-5). My s t u d i e s i n b i r d s , s i m i l a r t o t h o s e i n many vertebrates  ( f o r r e v i e w see M c C l e l l a n , 1986), have  demonstrated  t h a t e l e c t r i c a l s t i m u l a t i o n o f t h e p o n t o b u l b a r locomotor (PLS) e l i c i t s l o c o m o t i o n i n b i r d s . The e l e c t r i c a l l y locomotion  strip  induced  ( w a l k i n g a t t h r e s h o l d ) can be m a i n t a i n e d over  c o n s i d e r a b l e p e r i o d s (>10 minutes)  (Steeves e t a l . ,  1987; Funk  et a l . , submitted), thereby i n d i c a t i n g t h a t the locomotion i s not s i m p l y a t r a n s i t o r y escape b e h a v i o u r . I n b i r d s , as i n mammals, t h e s t i m u l a t i o n l o c u s l i e s w i t h i n t h e TTD and s t r o n g l y i m p l i c a t e s t h i s r e g i o n as b e i n g synonymous w i t h t h e PLS (Jordan, 1986; G a r c i a - R i l l and S k i n n e r , 1986; Noga e t a l . ,  1 9 8 8 ) ( F i g s . 1,  Chapters 3-5). Furthermore, l o c o m o t i o n can be evoked by t h e  268  introduction picrotoxin As  o f neurochemicals  elicited  3, i n t r a - T T D c h o l i n e r g i c a g o n i s t  long l a s t i n g  inputs f o r this  pontine  and m e d u l l a r y  locomotion i n b i r d s .  cholinergic  reticular  parabrachial  innervation  raphe  r e g i o n , w h i l e TTD i t s e l f  CHAT-containing Although  pallidus  remain 4,5).  from t h e  and t h e  neurons.  s e v e r a l p o t e n t i a l pathways f o r c h o l i n e r g i c  control  e f f e c t s produced  with  o f GABAergic and g l u t a m a t e r g i c a n t a g o n i s t s / a g o n i s t s  without  a strong neuroanatomical  GABA-containing  localized  cell  t o TTD i n mammals  (Mugnaini  GABA p l a y s some r o l e ,  down-regulating  afferent  A role  substrate  and O e r t e l , possibly  possibly  1985),  selectively  i n f o r m a t i o n , i n locomotor  f o r glutamate,  (Chapters  b o d i e s a n d r e c e p t o r s have b e e n  suggesting that  TTD.  arise  encompasses  TTD have b e e n p o s t u l a t e d , t h e l o c o m o t o r  injection  The most  formation, the descending  v e s t i b u l a r nucleus, the nucleus  of  (carbachol,  a n d NMDA) i n t o TTD.  d i s c u s s e d i n Chapter  injection likely  of a variety  control v i a  antagonistic to that of  GABA, may a l s o be p o s t u l a t e d ( C h a p t e r 5 ) . The  above r e s u l t s  i n birds,  other vertebrates ( G r i l l n e r , and that  Skinner,  1986; J o r d a n ,  taken together with those  1976; A r m s t r o n g ,  1986; G a r c i a - R i l l  1986; Noga et al., 1988),  t h e PLS a n d TTD r e g i o n a r e e q u i v a l e n t . F u r t h e r ,  neuroanatomical intimately therefore  connections suggest  that  associated with a variety s e r v e a s an i n t e g r a t o r y  information affects  ongoing  269  suggest i t s  t h e TTD r e g i o n i s  o f s e n s o r y i n p u t s a n d may  c e n t r e through which  locomotor  from  sensory  output. This hypothesis  s u p p o r t s t h e h y p o t h e s i s o f Noga e t al.  (1988), which s t a t e s t h a t  P L S / t r i g e m i n a l / l a t e r a l r e t i c u l a r f o r m a t i o n system  "provides a  substrate f o r sensorimotor r e f l e x i n i t i a t i o n of locomotion". F u r t h e r support f o r and e x t e n s i o n o f t h i s h y p o t h e s i s comes from a study d e s i g n e d t o determine whether p h a s i c p e r i p h e r a l a f f e r e n t i n f o r m a t i o n i s e s s e n t i a l f o r t h e p r o d u c t i o n o f locomotor patterns i n birds. In t h e study  (Chapter 6 ) , I examined t h e r o l e o f p h a s i c  a f f e r e n t feedback by comparing t h e locomotor p a t t e r n s o f animals p r i o r t o and f o l l o w i n g p a r a l y z a t i o n . My r e s u l t s i n d i c a t e t h a t a f f e r e n t i n p u t i s n o t e s s e n t i a l f o r t h e p r o d u c t i o n o f t h e wide a r r a y o f a v i a n locomotor p a t t e r n s i n b o t h h i g h d e c e r e b r a t e spontaneously electrical  l o c o m o t i n g o r i n s t i m u l a t e d ( c h e m i c a l and  s t i m u l a t i o n ) p a r a l y z e d a n i m a l s . One o f t h e r e s u l t s o f  t h e study was t h a t l o c o m o t i o n c o u l d be e l i c i t e d by t r i g e m i n a l f i e l d s t i m u l a t i o n i n b i r d s which p r e v i o u s t o p a r a l y z a t i o n were spontaneous, activity.  b u t a f t e r p a r a l y z a t i o n d i d n o t show any spontaneous  This f i n d i n g , together with the r e s u l t that increased  s t i m u l a t i o n i n t e n s i t y was n e c e s s a r y t o i n i t i a t e l o c o m o t i o n  after  p a r a l y z a t i o n i n low d e c e r e b r a t e a n i m a l s , suggests t h a t a f f e r e n t i n p u t may not o n l y i n i t i a t e r e f l e x l o c o m o t i o n , but may a l s o serve t o s e t the animal's o v e r a l l a c t i v a t i o n l e v e l f o r locomotion. I f p e r i p h e r a l a f f e r e n t input serves t o set the activation level,  TTD may w e l l s e r v e as t h e i n t e g r a t o r y c e n t r e  for the information. The r e s u l t s o f s t u d i e s p r e s e n t e d i n t h i s t h e s i s s t r o n g l y suggest t h a t b i r d s , l i k e mammals (Armstrong,  270  1986), possess a  h i e r a r c h i c a l system o f locomotor c o n t r o l . The lowest  l e v e l of  the h i e r a r c h y i s found i n t h e s p i n a l c o r d LPG. The LPG appears to be c o n t r o l l e d both by a f f e r e n t input and, more i m p o r t a n t l y f o r v o l u n t a r y locomotion, brainstem  v i a r e t i c u l o s p i n a l input from the  r e t i c u l a r formation n u c l e i (Cnd & Cnv). In t u r n ,  c o n t r o l i s exerted on the r e t i c u l o s p i n a l neurons by (e.g. v i a TTD) and c e n t r a l l y generated input mMRF,). C e n t r a l s t r u c t u r e s themselves b a s a l ganglia)  sensory  (e.g. RP, ICo,  (e.g. subthalamic  region,  appear t o be under higher l e v e l s o f c o n t r o l from  l i m b i c and t e l e n c e p h a l i c r e g i o n s . The  g e n e r a l impression  avian l o c o m o t i o n - r e l a t e d are s i m i l a r t o those  o f my s t u d i e s s t r o n g l y suggests t h a t  s t r u c t u r e s and t h e i r  interconnections  found i n both h i g h e r and lower v e r t e b r a t e s .  T h i s s i m i l a r i t y i s d i s c u s s e d throughout the t h e s i s 1-7).  (Chapters  While the n e u r a l c i r c u i t r y which comprises the h i e r a r c h y  appears t o have been h i g h l y conserved d u r i n g the e v o l u t i o n a r y process,  c o n s i d e r a b l y more i n f o r m a t i o n i s r e q u i r e d f o r the  understanding  o f n e u r a l locomotor c o n t r o l mechanisms.  However, i n l i g h t o f the c u r r e n t l y a v a i l a b l e techniques, b e l i e v e t h a t the study  I  o f motor c o n t r o l has reached a p o i n t from  which i t w i l l now be p o s s i b l e t o d e f i n e and manipulate a l l o f the major n e u r a l pathways i n v o l v e d i n locomotor c o n t r o l . Techniques such as neuroanatomical t r a c i n g , both r e t r o g r a d e and anterograde,  make i t p o s s i b l e t o d e f i n e e f f e c t i v e l y the a f f e r e n t  and e f f e r e n t connections Jordan,  o f every b r a i n r e g i o n  (Steeves and  1984; G a r c i a - R i l l et a l . , 1983a; Webster and Steeves,  1988). Immunohistochemistry allows d e s c r i p t i o n o f some o f the  271  neurotransmitters u t i l i z e d i n p r e p a r a t i o n ) . Receptor  by t h e s e pathways autoradiography  r e c e p t o r s p r e s e n t b o t h p r e - and  postsynaptically  (Dietl  us t o r e c o r d f r o m (Orlovsky,  vivo  microdialysis  activity. infusion  1988). E l e c t r o p h y s i o l o g y a l l o w s  n e u r o n s t o examine t h e i r  1970a, 1972b,c; G a r c i a - R i l l  neurotransmitter  (Phillips  selective  the process  Noga e t al.,  (Chapters  1988). While  in  changes i n  regions during  neurochemical  thesis,  I have a t t e m p t e d of avian  and m a n i p u l a t i o n o f l o c o m o t o r  increase the understanding  and have p r e d i c t i v e v a l u e  to utilize  this  of a c o r t i c o s p i n a l f o r t h e study  from  o f locomotor  f o r future studies. integrated  In t h i s  approach i n  locomotion.  a t t r i b u t e s which t h e b i r d possesses, locomotion,  al.,  though  of information gathered  control  study  et  3-5/ G a r c i a - R i l l  these techniques,  allow f o r the d e f i n i t i o n  these techniques w i l l  bipedal  specific  intracerebral  pathways, o n l y t h e i n t e g r a t i o n  The  1988) and  o f n e u r o t r a n s m i t t e r a g o n i s t s and a n t a g o n i s t s a l l o w s us  powerful,  the  and S k i n n e r ,  activity  e t a l . , 1988) d e t e r m i n e s  c o n c e n t r a t i o n s from  Finally,  to manipulate 1985;  individual  al.,  d e f i n e s some o f t h e  neurotransmitter  e t al.,  et  (Taccogna  including i t s  two s e p a r a t e modes o f l o c o m o t i o n tract  make t h e b i r d  an e x c e l l e n t  o f many a s p e c t s o f l o c o m o t i o n .  272  and a b s e n c e animal  model  CHAPTER 9 LIST OF REFERENCES  273  Adams R.D. 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A s s e n , The N e t h e r l a n d s p p l - 1 4 8 .  290  APPENDIX I Neurochemical Injection Parameters f o r Altering L o c o m o t i o n Experimenters Animal  Garcia-Rill •t al., 1985  Garcia-Rill a Skinner. 19B7a  Site  decerebrate PPN oat (mMLR)  decerebrate PPN cat NRV NRG NRV NRV NRV NRG  Chemical  pH  Concentrations Injected  Lowest Volume Effective Concentration  acetylcholine  4-7  1mM-1M  none  I.Sul  <1-2ul/min  GABA picrotoxin bicuculline muacimo! diazepam ttrychnine  4-7  O.SM (T) SmM SmM 5mM (Til) 5mM (T) none  1.5ul 1.S-3ul I.Sul I.Sul I.Sul I.Sul  ••  <1  ••  " "  0.6-1M 1-5mM SmM 6mM 1-5mM 5-10mM  3.4 na <5 na  3-5 20-60 na >15 1-5  —  —  glutamate  4-7.5  8mU-1M  1.0M (RT)  1.5ul  ••  —  —  norepinephrine 4-7 *' dopamine  50mm-1M 100mM-1M  none none  I.Sul I.Sul  ••  —  —  —  —  picrotoxin  4-7  1-5mM  ImM  1.5ul  1ul/min  tee above results  acetylcholine carbachol atropine edrophonium etarine methacholino  '•  lul/min  " "  0.1-0.6M 10uM-1mM 10-100uM  O.SM 1-10uM 1uM-1mM 100mM 100-500uM 10-100uM  ••  "  0.2-1M 1uM-1mM 1uM-1mM  1-3 1-5 na 2-3 2-3 1-5  5-60s 1-5 1-2h 1-5 1-5 1-5  1S-30S  2-5 — —  NRV NRG NRG NRG  GABA picrotoxin  NRG NRG  glutamate aspartate  NRV  Substance P  "  bicuculline muscimol ••  Eldridga et al.. 1886  decerebrate SLR cat SLR  picrotoxin muscimol  Noga et al, 1S88  deoerebrate MRF MRF cat MRF  GABA picrotoxin muscimol  7.2-7.5  MRF MRF  glutamate DL-HCA  ••  na na  "  0.2-0.5M 1-5mM 100uM-5mM  Rate  •• ••  " ••  ••  " "  1-5mM  0.2M 5mM (C) 5mM (C) 1mM  0.5-1M 0.5-1M  0.5M (NR) 0.5M (NR)  0.5-5mM  0.5mM  ••  8mM 44 mM  8mM 44mM  S-IOmM 6-10mM 5-10mM 5-100mM 0.1M  — —  na  1-3h  ••  —  —  "  —  —  ••  1S-30S  15-30.  Sul 6ul  na na  15 20  45 na  na SmM (RT) na  Sul 6ul Sul  1ul/min ••  "  S — 5  10-16 15-25 irr. block  lOOmM 0.1M (RT)  Sul Sul  30  "  —  100 15-25  PLS  picrotoxin  ••  6-10mM  10mM  lul  ••  2-20  20-80  PLS PLS PLS  glutamate GDEE DL-HCA  ••  100mM 100mM lOOmM  Sul Sul 7ul  ••  "  6-100mM 6-100mM lOOmM  na 12 4  15-20 IS na  "  PLS  Substance P  •  0.74mM  0.74 mM  Sul  Brudzynski A Mogenoon, 1S88  intact rat  AH/LPA  carbachol atropine  na na  65mM 11.1mM  S5mM 11mM  0.2ul 0.4ul  0.4ul/min  Brudzyntki A Mogenson, 1988b  intact rat  AH/LPA AH/LPA  carbachol atropine  8.5-7.0  27.4mM 11.1mM  27.4mM 11.1mM  0.2ul  0.4ul/min  N.Acc  amphetamine  583mM  583mM  "  PPN PPN  carbachol atropine  B.0-7.0  27.4mM 11.1mM  27.4mM 11.1mM  0.2 ul  N.Acc  amphetamine  ••  683mM  acetylcholine carbachol atropine  na na na  glutamate NMDA kainate quisqualate GDEE APV  na na na na na na  Brudzyntki et intact al.. 1988 rat  Lai and Siegel. 1888  Time Course (min) Latency Period  decerebrate NMC cat A NPM  1-2  30  5 na  na na  <1 <1  S S  <1  S >7  '•  3-5 na  683mM  ••  na  na  1.1M 44-1 OOmM 7mM  na na na  O.Sul  0.5ul/min  "  ••  na na na  na na na  0.05-0.4M 1-4-6.8mM O.BuM-O.BmM 0.2-0.SmU 200mM SOmM  na na na na na na  na na na na na na  na na na na na na  291  ••  0.4ul/min  M  -  "  ••  '•  "  •• ••  na  E x p e r i m e n t * ™ Animal  Site  Sholomenko Thesis. 1989  Acetylcholine Agonists and Antagonists TTD  Concentration! Injected  Lowest Volume Effective Concentration  1.0ul  Rale  Time Course (min) Latency Period  0.2ul/min  2.2-12 — — 8 7 3.3-6 — <5  7-45 — — 25 8 33 — >26  2.2-6 — —  7-45 — —  >7.5 —  21-40  "  2SmM-100mM 2SmM 26mM 2SmM SOmM 11mM-100mM 2SmM 30mM  2SmM none none 25mM none 11 mM none 30mM  Carbachol 7.2-7.4 Scopolamine " Nicotine " Atropine " Pilocarpine "  27-100mM 25mM 100mM 3-50mM SOmM  27mM none none 20mM none  RP  Carbachol  "  64mM  none  "  ••  —  —  MRP  Carbachol  "  lOOmM  100mM (RT)  "  ••  —  45  MLF  Carbachol  "  27-10OmM  27  ••  8-10  23-40  1-S 4-22 15 5-10  2-21 35-60 >30 30-70  "  none none  none none  "  <1 4-22 >9  9-14 30 >30  <1 10 —  12-21 36 —  ••  <1 11-13  2-12 >30  Cnv  ••  " "  •• M  ••  " ••  " "  —  GABAergic agonists and antagonists TTD  Cnd Cnv  RP  MRF  Sholomenko Thesis. 1989  pH  Carbachol 7.2-7.4 Scopolamine " Nicotine " Atropine Pilocarpine " Carbachol Scopolamine Atropine  Cnd  Sholomenko Thesis. 19SS  Chemical  0.3-0.SM 3-20mM 10mM 6.5-25mM  O.SM 3mM 10mM 6.5mM  I.QuI  0.2ul/min  " "  "  " "  5mM 6.2SmM  none none  "  " "  O.SM 6-20mM 8.25mM  O.SM 6mM 6.25mM  ••  GABA Picrotoxin Muscimol  " "  O.SM 3-6mM 6.2SmM  O.SM 3mM none  "  GABA Picrotoxin  "  O.SM 6-20mM  O.SM SmM  GABA Picrotoxin Bicuculline Muscimol  7.2-7.4  Picrotoiin Muscimol GABA Picrotoxin Muscimol  ••  ••  •• ••  Excitatory Amino Acids and Substance P TTD-  Glutamate NMDA GDEE Substance P  "  "  0.5-1.OM SOmM 2-80mM 6.44mM  none SOmM 2mM none  I.Oul 0.2ul 0.4-1 ul I.Oul  — <1 4-6  —  —  —  <1.S <5  3-24 >35 —  10 35-55  Cnd  NMDA GDEE Substance P  20-83mM SOmM 8.44mM  20mM SOmM none  0.2ul 0.6ul I.Oul  —  Cnv  Glutamate NMDA GDEE Substance P  1M 4-83mM 2-80mM S.44mM  none 4mM 2mM none  I.Oul 0.4ul 0.2ul I.Oul  <1 4-6 —  35-50 —  81-83mM 6.44mM  83mM 6.44 mM  0.2ul I.Oul  <1-1.25 4  4-9 >1S  "  — 3-4  RP  NMDA 7.2-7.4 Substance P  MRF  NMDA  6-34mM  6mM (RT)  0.2ul  5  15  MLF  NMDA  20-34mM  34mM  0.4 ul  <1  8  292  ABBREVIATIONS: Appendix I AH  —  anterior  C  —  convulsant  hypothalamus  Cnd  —  dorsal part, medullary central  Cnv  —  ventral part, medullary central  h  —  hours  nucleus nucleus  I  —  irreversible  irr. b l o c k  —  irreversible  LPA  —  lateral preoptic  MLF  —  medial longitudinal  mMLR  —  medial m e s e n c e p h a l i c locomotor region (see  mrf  —  medial reticular formation  MRF  —  mesencephalic reticular  na  —  not available  N.Acc  —  nucleus  NMC  —  magnocellular reticular  NPM  —  paramedian  NR  —  no r e p e a t a b l e  NRG  —  gigantocellular reticular  NRV  —  ventral reticular  PLS  —  block area fasciculus PPN)  (medulla)  formation  accumbens formation  nucleus response formation  formation  p o n t o b u l b a r locomotor strip —  e q u i v a l e n t to the d e s c e n d i n g t r i g e m i n a l  a n d nucleus together with the adjacent parvocellular reticular formation PPN  —  pedunculopontine nucleus (see  mMLR)  RP  —  pontine reticular  RT  —  r e d u c e d t h r e s h o l d for e l e c t r i c a l l y s t i m u l a t e d  nucleus  s  —  seconds  SLR  —  subthalamic locomotor  TTD  —  descending trigeminal tract and  region nucleus  , 293  locomotion  tract -  APPENDIX II RESPIRATORY AND CARDIOVASCULAR VALUES IN DECEREBRATE AND INTACT CANADA GEESE  INTACT  DECEREBRATE  Rest  n  Exercise  %Ctange  n  Rest  n  Ex6TCtS6  %Change  V  £  (mt/min/Kg)  314±28  13  448*27 #  42.2  13  417*30  21  887*65 #•  119  V  T  (ml/Kg)  29.9*1.5  13  34.1*2.3  14.6  13  28.2*1.3  21  26.5*2.4  •4.6  10.7*1.0  13  13.4*0.8  25.2  13  14.8*0.80  21  34.9*3.0 # *  137  f (min' ) 1  ymin  )  57.5*5.0  55.2*2.3  13  V (ml/min/Kg)  11.3*0.8  8  15.9*1.1 #  46.2  9  13.5*1.5  9  32.7*3.8 # *  V^fml/min/Kg)  7.6*0.7  8  12.6*0.6 #  68.3  S  13.1*1.3*  9  29.9*3.8 # *  0.6710.03  8  9  0.98*0.04 • 9  0.91*0.03  40.4*0.7  S  40.6*0.6  2  42.3  42.7  28.9*3.3  9  02  V° > c  Ent%  0.8*0.03 #  4  340*28'  47.7  164*7  3  162*9'  11.0  (R = 0.787)  18.48  (R = 0.985)  24.74  (R = 0.988)  18.67  (R = 0.982)  93.4 * 7.1  8  94.9 * 7.3  8  89.0  1  103.0  24.9*1.2  12  23.9*0.9  12  27.5  1  24.5  7.50*0.02  12  7.54*0.02  12  7.52  1  7.56  198*24  12  207*21.5  4.5  BP.  69*4.0  4  108.3*6.6  21.7  24.43  s  t o p  E^ 02 V  ,v /v E  C 0 2  28.3*4.0 264 * 28  Hesrtrate (min  S t o p e V  2  12  Blood Oases P  eO2  P  B C O 2  ( m m H 0  '  (mmH0)  Appendix M: Respiratory vatues in decerebrate and mtsct Canada Qoese recorded prior to and over the last 4 minutes of a 10minuta (decerebrate) and 6 minute (intact) walking period, (mean ± S.E.) n  =  number of experiments  % Change; percent change from rest to exercise. # ; significant difference between rest and exercise wtthm a group. *I Significant difference between the two groups during rest and exercise. mtnute vanttatton tidal volume f^; breathing frequency f^; stride frequency V j ^ ; C » production 2  V  02' ^2 P" ^* 30  128  00  T^; body ternperature. R* Pearson's Correlation Coefficient t  I*, not tested lor significant difference  294  n  

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