UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Tolerance to the anticonvulsive effect of alcohol is not influenced by Pavlovian conditioning Puttaswamaiah, Sheela D. 1984

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1984_A8 P88.pdf [ 3.73MB ]
Metadata
JSON: 831-1.0096386.json
JSON-LD: 831-1.0096386-ld.json
RDF/XML (Pretty): 831-1.0096386-rdf.xml
RDF/JSON: 831-1.0096386-rdf.json
Turtle: 831-1.0096386-turtle.txt
N-Triples: 831-1.0096386-rdf-ntriples.txt
Original Record: 831-1.0096386-source.json
Full Text
831-1.0096386-fulltext.txt
Citation
831-1.0096386.ris

Full Text

TOLERANCE TO THE ANTICONVULSIVE EFFECT OF ALCOHOL IS NOT INFLUENCED BY PAVLOVIAN CONDITIONING By Sheela D. Puttaswamaiah B. Sc. , Carleton University. 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n T H E F A C U L T Y O F G R A D U A T E S T U D I E S (Department of Psychology) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH1' COLUMBIA August 1984 ©Sheela D. Puttaswamaiahi 1984 . f*> \ •» In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements fo r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I further agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of P s y c h o l o g y The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date ' August 1-5, 198*f DE-6 (3/81) i i ABSTRACT Tolerance to the Anticonvulsive E f f e c t of Alcohol i s not Influenced by Pavlovian Conditioning by Sheela D. Puttaswamaiah The e f f e c t s of environmental manipulations on the duration of kindled seizures e l i c i t e d by amygdaloid stimulation were measured to determine i f tolerance to the anticonvulsive e f f e c t of alcohol could be explained by the Pavlovian model of drug tolerance. Experiment 1 was conducted to determine i f tolerance to the anticonvulsive e f f e c t of alcohol i s context s p e c i f i c . Rats with kindled seizures received f i v e b i d a i l y alcohol i n j e c t i o n s i n Environment A a l t e r n a t i n g with f i v e b i d a i l y s a l i n e i n j e c t i o n s i n Environment B, each followed 1 hr l a t e r by an amygdaloid stimulation. On the t e s t day* h a l f the subjects received the t e s t i n j e c t i o n and stimulation i n the alcohol-associated environment (Environment A) whereas the other h a l f received the t e s t i n j e c t i o n and stimulation i n the saline—associated environment (Environment B). No s i g n i f i c a n t d i f f e r e n c e s i n seizure a c t i v i t y between the two groups were seen. The subjects r e c e i v i n g the t e s t i n j e c t i o n i n Environment A were given s a l i n e i n j e c t i o n s and stimulations i n t h i s same environment 48 hr a f t e r the alcohol t e s t i n j e c t i o n . Exposure to j u s t the a l c o h o l - p r e d i c t i v e cues d i d not e l i c i t a compensatory increase i n seizure a c t i v i t y as predicted from 0 i i i the Pavlovian model of drug tolerance. Experiment 2 was designed to show that e x t i n c t i o n procedures would produce an attenuation of tolerance to the anticonvulsive e f f e c t of alcohol. Subjects were given b i d a i l y a lcohol i n j e c t i o n s and stimulations i n Environment A f o r f i v e sessions. The subjects i n the ex t i n c t i o n condition were then given f i v e b i d a i l y s a l i n e i n j e c t i o n s and stimulations i n Environment A, whereas the c o n t r o l subjects were given only stimulations on these f i v e days, but i n an environment not associated with alcohol. On the t e s t day, a l l subjects received an alc o h o l i n j e c t i o n and stimulation i n Environment A. Although the two groups did not d i f f e r s i g n i f i c a n t l y i n seizure duration, they both exhibited seizure durations so close to zero that observing any further attenuation of tolerance i n the group that had undergone the ex t i n c t i o n procedures would not have been possible. Accordingly, i t cannot be claimed that the e x t i n c t i o n procedures af f e c t e d tolerance to the anticonvulsive e f f e c t of alcohol, however the l e v e l of tolerance i n the c o n t r o l group diss i p a t e d so r a p i d l y that i t i s u n l i k e l y that learning played a r o l e i n i t s development. In Experiment 3, the e f f e c t of CS (conditioned s t i m u l i ) preexposure on the development of tolerance to the anticonvulsive e f f e c t of alcohol was investigated. Subjects i n the Preexposure Group were given f i v e b i d a i l y s a l i n e i n j e c t i o n s and stimulations i n Environment A — subsequently to be associated with alcohol administration. Control group subjects were given the same treatment but i n Environment B. During the tolerance development sessions and the t e s t session, a l l r a t s were given f i v e b i d a i l y alcohol i n j e c t i o n s and stimulations i n Environment A. CS prexposure did not retard the development of tolerance to the anticonvulsive iv e f f e c t of alcohol. These r e s u l t s i n d i c a t e that, tolerance to the anticonvulsive e f f e c t of alcohol can develop i n the absence of conditioning effects. This study constitutes the f i r s t systematic demonstration of the f a i l u r e to v e r i f y the Pavlovian model of tolerance« thus l i m i t i n g the generality of the model. V TABLE OF CONTENTS Introduction 1 D e f i n i t i o n s of* Tolerance 2 Pavlovian Theory of Learned Tolerance 3 Contingent Tolerance and the Anticonvulsive E f f e c t of Alcohol 12 Rationale 16 General Methods 17 EXPERIMENT 1 S i t u a t i o n a l S p e c i f i c i t y and Tolerance to the Anticonvulsive E f f e c t of Alcohol Introduction 22 Methods 22 Results 25 Discussion 30 EXPERIMENT 2 Ex t i n c t i o n of Tolerance to the Anticonvulsive E f f e c t of Alcohol Introduction 31 Methods 31 Results 33 Discussion 36 EXPERIMENT 3 The E f f e c t of CS Preexposure on Tolerance to v i the Anticonvulsive E f f e c t of Alcohol Introduction 37 Methods 38 Results 39 Discussion 42 Histology and Blood Alcohol Analysis 43 General Discussion 51 Interpretation of the Results 52 Major Implications of the Conclusions 55 Concluding Remarks 64 References. . 67 LIST OF FIGURES Figure i Tolerance to the anticonvulsive e f f e c t of alcohol i s not s i t u a t i o n s p e c i f i c 28 Figure 2 The e f f e c t of e x t i n c t i o n procedures on tolerance to the anticonvulsive e f f e c t of alcohol 35 Figure 3 CS preexposure does not attenuate the development of tolerance to the anticonvulsive e f f e c t of alcohol. . 41 Figure 4 Figure 5 Figure 6 Electrode placements of subjects i n Experiment 1. . . 46 Electrode placements of subjects i n Experiment 2. . . 48 Electrode placements of subjects i n Experiment 3. . . 50 v i i i LIST OF TABLES Table 1 Studies i n v e s t i g a t i n g Pavlovian conditioning of tolerance to d i f f e r e n t e f f e c t s of d i f f e r e n t drugs. ... 9 Table 2 Blood alcohol l e v e l s of subjects i n Experiments 1# 2, and 3 44 ACKNOWLEDGEMENTS I would l i k e to l i k e thank Dr. John P i n e l f o r h i s support throughout the duration of these experiments and h i s assistance i n the preparation of t h i s thesis. I would also l i k e to thank Michel Mana and George Renfrey f o r t h e i r invaluable assistance i n performing some of the experiments. 1 Introduction The case of a 24 year old woman recently admitted to the UCLA Medical School h o s p i t a l complaining of abdominal pain was described by Johnson* Noll* and Rodney (1982). What i s remarkable about t h i s case i s that despite the f a c t that her blood alcohol l e v e l was 1510 mg/dl* the highest ever recorded* she was f u l l y conscious and had no obvious symptoms other than tremors and abdominal pain. Apparently the a b i l i t y of t h i s woman to withstand the e f f e c t s of such a high blood alcohol concentration — the usual l e t h a l dose i s between 400 and 500 mg/dl ( S e l l e r s & Kalant* 1976) — was a consequence of the f a c t that she had been int o x i c a t e d f o r much of the 9-month period preceding her admission. Accordingly* t h i s c l i n i c a l case provides a p a r t i c u l a r l y s t r i k i n g * a l b e i t uncontrolled* demonstration of the phenomenon of drug tolerance* that is* i t i s a demonstration that one or more e f f e c t s of a drug have been reduced as a r e s u l t of p r i o r exposure to i t . The studies comprising t h i s t h e s i s are a l l studies of drug tolerance. In particular* they are a l l studies of tolerance to the anticonvulsive e f f e c t of alcohol and of the e f f e c t of learning on i t s development. Accordingly* the f i r s t three sections of the introduction w i l l include (a) a d e f i n i t i o n of drug tolerance and a b r i e f discussion of the types of fa c t o r s that can influence i t s development* (b) evidence that learning can influence the development of tolerance to alcohol* and (c) a discussion of contingent tolerance to a l c o h o l x s anticonvulsive effect. The introduction concludes with a statement of the s p e c i f i c purpose of the thesis. 2 De f i n i t i o n s of Tolerance Tolerance to a drug i s said to have occurred when as a consequence of previous exposure to the drug, there i s a decrease i n the e f f e c t of a p a r t i c u l a r dose of the drug and an increase i n the dose necessary to produce a p a r t i c u l a r effect. In other words, tolerance to a drug i s s a i d to have occurred when the dose-reponse curve has s h i f t e d to the r i g h t as a consequence of exposure to that drug (Cicero, 1980; LeBlanc, Kalant, & Gibbins, 1975). I t i s common to d i s t i n g u i s h between three types of changes that might underlie any p a r t i c u l a r instance of drug tolerance metabolic changes, p h y s i o l o g i c a l changes, or learned changes. In other words, i t i s commonly recognized that tolerance e f f e c t s can r e s u l t (a) from an increase i n the rate of elimination of the drug from the body as a whole or from c r i t i c a l s i t e s , (b) from a change i n the s e n s i t i v i t y of the c e n t r a l nervous system or other t i s s u e s to p a r t i c u l a r actions of the drug, or (c) to learned responses that counteract the e f f e c t s of the drug. I t i s important not to overlook two i m p l i c i t implications of t h i s three-category view of drug tolerance. The f i r s t i s that any p a r t i c u l a r instance of tolerance might be a t t r i b u t a b l e to any one of these mechanisms or* f o r that matter* to any combination of them. The second i s that the category of learned tolerance i s not e n t i r e l y exclusive of the other two categories. Presumably metabolic and/or p h y s i o l o g i c a l changes mediate any e f f e c t s that l e a r n i n g has on the development of drug tolerance. Be that as i t may, i t i s usual to assume that metabolic and p h y s i o l o g i c a l mechanisms underlying tolerance can be 3 influenced only by changing the amount of drug exposure* and thus that the e f f e c t s of learning on tolerance can be established by demonstrations i n which manipulations of the external environment influence tolerance development. The focus of the present t h e s i s i s on the p o t e n t i a l e f f e c t s of learning on drug tolerance. The term "behavioural tolerance" i s sometimes used as a synonym f o r learned tolerance* however t h i s use appears to r e s u l t from a f a i l u r e to c l e a r l y d i f f e r e n t i a t e between the measures used to assess tolerance development on the one hand and the mechanisms that are assumed to underlie i t on the other. According to Kayan* Woods* and M i t c h e l l (1969). who coined the term* behavioural tolerance r e f e r s simply to a decrease i n some behavioural e f f e c t of a drug with repeated exposure. C l e a r l y such behavioural changes can be accounted f o r j u s t as r e a d i l y by d i r e c t metabolic or p h y s i o l o g i c a l changes as they can by learning* j u s t as tolerance to a p h y s i o l o g i c a l drug e f f e c t <e. g. * hypoglycemia) can be accounted f o r by learning. Thus* behavioural tolerance r e f e r s to a type of tolerance effect* whereas learned tolerance r e f e r s to one p a r t i c u l a r mechanism by which tolerance can develop. Confusing the two terms tends to cloud the issues. Pavlovian Theory of Learned Tolerance, The s o - c a l l e d Pavlovian theory of learned tolerance i s an extension of Solomon vs opponent process theory (1972* 1973). Solomon proposed that the p h y s i o l o g i c a l e f f e c t of drug administration (process A) eventually a c t i v a t e s changes (process B) that appose the i n i t i a l drug effects* thus leading to tolerance. According to the o r i g i n a l * Pavlovian view of 4 tolerance proposed by Sieg e l (e. g. 1975), pharmacological stimulation of the drug i s the unconditioned stimulus (UCS). When these UCSs are repeatedly e l i c i t e d i n the presence of the same environmental cues (conditioned stimuli, CSs), these cues begin to e l i c i t conditioned responses (CRs), opposite i n d i r e c t i o n to the i n i t i a l e f f e c t s of the drug (unconditioned responses, UCRs). As the conditioned compensatory responses increase i n magnitude, they progressively counteract the i n i t i a l e f f e c t s of the drug and r e s u l t i n drug tolerance. Although i t i s usual to r e f e r to t h i s theory of drug tolerance as the Pavlovian theory of tolerance (e.g. Crowell, Hinson, & Siegel, 1981; Poulos, Wilkinson, & Cappell, 1981; Siegel, i n press), i t i s not s t r i c t l y consistent with Pavlovian theory. There i s a major discrepancy with regard to the i d e n t i t y of the CR. According to Pavlov (1927/1960), the CR i s always i n the same d i r e c t i o n as the UCR. However, according to Siegel*s s o - c a l l e d Pavlovian theory of drug tolerance, a CR develops that counteracts the unconditioned e f f e c t s of the drug. In a more recent report, however* S i e g e l (in press)- has revised h i s theory such that the UCS xs are the c e n t r a l e f f e c t s of the drug and the UCRxs are the systemic responses e l i c i t e d by the drug. The CS and CR remain the same as i n the o r i g i n a l version of t h i s theory. Three types of experiments are commonly used to support Siegel " s account of drug tolerance. Although most of the support f o r t h i s Pavlovian theory has been provided by studies of morphine tolerance, comparable experiments have recently suggested that i t applies equally well to at l e a s t some manifestations of alcohol tolerance. Because the studies reported herein are a l l studies of alcohol tolerance, the following discussion of the types of experiments supportive of Siegel 1 1 s theory, w i l l be r e s t r i c t e d to studies of alcohol 5 effects. One type of evidence f o r the Pavlovian i n t e r p r e t a t i o n comes from demonstrations of s i t u a t i o n a l s p e c i f i c i t y , that i s , demonstrations that tolerance to a drug i s manifested f u l l y only when the drug i s administered i n the environment that has previously predicted i t s presentation. A number of studies have demonstrated s i t u a t i o n a l s p e c i f i c i t y f o r some types of alcohol tolerance. In one such study, Le> Poulos, and Cappell (1979) i n j e c t e d r a t s i n t r a p e r i t o n e a l l y with 2. 5 g/kg alcohol once every 2 days f o r 18 days. These nine alcohol administrations took place i n a room made d i s t i n c t i v e by dim i l l u m i n a t i o n and by the sound of s t a t i c from a radio. By the ninth t r i a l , the mean hypothermic response to alcohol was much smaller than that e l i c i t e d by the f i r s t i n j e c t i o n . On the 10th and 11th sessions, the subjects were i n j e c t e d with alcohol i n a d i s t i n c t i v e environment not previously associated with a l c o h o l and i n the alcohol-associated environment, respectively. On the 10th session, the mean hypothermic response was s u b s t a n t i a l l y l a r g e r than that on the 9th alcohol session, that i s , the subjects showed a l o s s of tolerance to alcohol's hypothermic e f f e c t when tested i n a novel environment. During the 11th session, subjects exhibited hypothermic responses s i m i l a r i n magnitude to those seen during the 9th alcohol session. C l e a r l y such demonstrations of s i t u a t i o n a l s p e c i f i c i t y provide strong support f o r the theory that environmental f a c t o r s are involved i n learned drug tolerance. In comparable studies, researchers have confirmed the s i t u a t i o n a l s p e c i f i c i t y of the hypothermic e f f e c t of alcohol i n r a t s (Crowell et al. , 1981; Mansfield & Cunningham, 1980) and found that the same holds f o r the hypothermic and hypnotic e f f e c t s of alcohol i n mice (Melchior & Tabakoff, 1980. 1981). 6 The second common type of experimental evidence f o r Siegel^s Pavlovian i n t e r p r e t a t i o n of alcohol tolerance comes from studies i n which s o - c a l l e d compensatory CRs have been e l i c i t e d by placebo i n j e c t i o n s administered i n the drug-associated environment. Three independent teams of investigators* Crowell et a l . (1981). Le et al. (1979). and Mansfield and Cunningham (1980)* have reported e l i c i t a t i o n of such a compensatory CR following development of alcohol tolerance. For example* Le et a l . (1979) demonstrated a conditioned compensatory hyperthermic response i n r a t s t o l e r a n t to the hypothermic e f f e c t of alcohol. The subjects were i n j e c t e d with alcohol every other day f o r 8 days i n the same environment. During the t e s t session* subjects received a s a l i n e i n j e c t i o n e i t h e r i n t h i s alcohol-associated environment or i n an environment not previously associated with alcohol (the home cage). Whereas the subjects r e c e i v i n g the placebo i n j e c t i o n i n the presence of non-alcohol cues showed small hypothermic responses* subjects r e c e i v i n g s a l i n e i n the presence of alcohol cues exhibited a compensatory hyperthermia. The t h i r d type of experimental evidence frequently offered i n support of S i e g e l x s Pavlovian i n t e r p r e t a t i o n of tolerance has been provided by experiments showing that e x t i n c t i o n procedures can f a c i l i t a t e the decline of drug tolerance. In one such alcohol study (Mansfield & Cunningham* 1980)* r a t s were i n j e c t e d once every 48 hr with e i t h e r alcohol or* on alternate t r i a l s * saline. During t h i s phase of the experiment* a l l subjects received a t o t a l of seven alcohol i n j e c t i o n s i n the alcohol—associated environment and seven s a l i n e i n j e c t i o n s i n the saline-associated environment. The two environments were d i f f e r e n t with respect to noise leve l * illumination* size* and smell. By the seventh alcohol 7 inje c t i o n / there was a s i g n i f i c a n t reduction i n the hypothermic e f f e c t of the alcohol on r e c t a l temperature. During the e x t i n c t i o n phase, subjects i n the e x t i n c t i o n group were given 13 b i d a i l y s a l i n e i n j e c t i o n s i n the alcohol-associated environment. and the c o n t r o l subjects received equivalent treatment but i n the saline-associated environment. Upon challenge with an alcohol i n j e c t i o n i n the alcohol-associated environment. subjects i n the e x t i n c t i o n group exhibited lower r e c t a l temperatures than the c o n t r o l subjects, that i s . the e x t i n c t i o n subjects had l o s t more of t h e i r tolerance to the hypothermic e f f e c t of alcohol than had the controls. In a subsequent demonstration of e x t i n c t i o n to the hypothermic e f f e c t of alcohol. Crowell et al. (1981) used a r e s t group as a control. After tolerance development, subjects i n the r e s t group were l e f t undisturbed i n t h e i r home cages while the experimental subjects received s a l i n e i n the alcohol-associated environment. Despite t h i s procedural difference. Crowell et a l . confirmed the f i n d i n g of Mansfield and Cunningham that s a l i n e i n j e c t i o n s i n the drug-related environment can contribute to a decline i n tolerance to a l c o h o l % s hypothermic effect. These three types of experiments—demonstrations of s i t u a t i o n a l s p e c i f i c i t y . compensatory CRs. and e x t i n c t i o n — h a v e (a) c l e a r l y established that the environment i n which a drug i s given can have a great e f f e c t on the development of tolerance to i t and (b) have l e n t a great deal of support to S i e g e l % s Pavlovian i n t e r p r e t a t i o n of such effects. In each experiment, animals r e c e i v i n g exactly the same pattern of alcohol and placebo i n j e c t i o n s displayed d i f f e r e n t degrees of tolerance depending upon the environment i n which the i n j e c t i o n s were given. Thus, the view that 8 repeated exposure to alcohol i s a s u f f i c i e n t condition f o r tolerance i s no longer tenable (LeBlanc, Kalant, & Gibbins. 1976). Although such studies have never been reported i n the l i t e r a t u r e on alcohol tolerance. support f o r Siegel*s Pavlovian theory of tolerance has also come from demonstrations that CS preexposure can retard the development of tolerance (see Table 1). For example, S i e g e l (1977) investigated the e f f e c t of CS preexposure on tolerance to morphine xs analgesic effect. I t i s known that exposure to the CS without simultaneous exposure to the UCS retards subsequent conditioning of the UCS with those CS xs (Lubow & Moore. 1959s Randich * LoLordo. 1979). Consequently, i f conditioning were to play a r o l e i n tolerance development, one might expect that exposure to the environment which would subsequently become the drug-associated environment would retard tolerance development. In a study to confirm t h i s prediction. S i e g e l (1977) i n j e c t e d one group of r a t s with s a l i n e and exposed them to a non-functional hot plate i n the future morphine-predictive environment. during the preexposure period. The c o n t r o l subjects were l e f t i n the home cage during the preexposure period. A f t e r undergoing the tolerance a c q u i s i t i o n period, i n which a l l subjects were i n j e c t e d with alcohol and subsequently tested i n the morphine-predictive environment, the c o n t r o l subjects exhibited greater tolerance than the preexposure subjects. Although descriptions of studies supportive of the Pavlovian theory of tolerance were confined to those i n v o l v i n g alcohol* there have been quite a number of studies i n v o l v i n g other drugs and measures not mentioned i n t h i s thesis. Table 1 summarizes recent examples of every tolerance e f f e c t that has been investigated with regard to i t s Pavlovian features. Table 1 Studies 1nvestIgating c l a s s i c a l condlt lontng of drug to Ierence Author Year Drug Subj ects Dependent Var table Ef fec t s Invest igated SS CR EX CS PR Pr Thompson & Ost lund K o r o l . S l e t t e n & Brown Wlkler & Pescor Lang,Rush & Pearson Roffman,Reddy, & Lai S1ege1 -S iege l Sk lar & Amlt Le .Poulos & Cappel1 Sherman S i e g e l . H l n s o n & Krank Mans f i e ld & Cunningham 1965 morphine rats 1966 atropine dogs 1967 morphine ra t s 1969 atropine dogs 1973 morphine rats 1975 Insul in rats 1977 morphine rats 1978 morphine rats 1979 ethanol rats 1979 morphine rats 1979 morphine rats 1980 ethanol rats amount of drug 1ngested sal 1 vat ion tremors sal 1 vat ion hyper therm 1 a hypoglycem1 a ana 1ges1 a— hot p late l e t h a l i t y hypotherm1 a hypertherm 1 a ana Iges 1 a lethal 1ty hypotherm1 a Table 1 (continued) Author Year Drug Subjects Dependent Ef fec t s Invest igated Var iab le SS CR EX CS PR Pr Cappel1.Roach & Poulos 1981 pento-b a r b i t a l rats hypothermia CrowelI .Hinson & Siege! 1981 ethanol rats hypothermia Etkelboom & Stewart 1981 morphine rats hyper therm 1 a Krank,H1nson S tegel Me)chior & Tabakoff 1981 morphine rats 1981 ethanol mice ana lges ia -paw 1 ick hypothermia sedat ion + + + Mucha,Vo1kov— sk i s & Kalant 1981 morphine rats 1ocomot ion Poulos ,Wi1 k t n— son, & Cappe11 198 1 d-amphet- rats amine anorex t a T i f f a n y & Baker 1981 morphine rats ana 1ges1 a— j unip | f 1 i nch Siege l Deme11 week & Goudie 1982 heroin rats 1983 d-amphet- rats am 1 ne morta1 1 ty anorex1 a T 1 f f a n y , P e t r le Mart in & Baker 1983 morphine rats analges i a -t a i l f l i c k Krank.Hinson & Stegel Wa1ter 6 R 1 cc i o 1984 morphine rats 1984 morphine rats ana 1ges1a-hot p la te ana 1ges1a-hot p la te Note : SS - S i t u a t i o n a l S p e c i f i c i t y CR — Compensatory CR EX - E x t i n c t i o n CS Pr - CS Preexposure PR — P a r t i a l Reinforcement + — This e f f e c t was demonstrated. x — This e f f ec t was tested but was not demonstrated. Blanks ind ica te that the e f fect was not tested in the study. 12 Contingent Tolerance and the Anticonvulsive E f f e c t of Alcohol In the previous section. the experimental support f o r S i e g e l x s i n t e r p r e t a t i o n of alcohol tolerance mas reviewed. Although there i s now strong support f o r such a view* i t i s c l e a r from Table I that only of few of a l c o h o l v s many e f f e c t s have been studied within the context of t h i s theory. In t h i s section. research about another e f f e c t of alcohol. i t s anticonvulsive effect, w i l l be described. Although there were some early reports of the e f f e c t s of repeated alcohol administrations on seizure a c t i v i t y (Dember. Ellen. & Kr i s t o f f e r s o n . 1953) Greenberg & Lester. 1953). a more recent one by Pinel. Colborne* Sigalet. and Renfrey (1983) was c r u c i a l to the design of the experiments comprising t h i s thesis. P i n e l et a l . (1983) f i r s t implanted a s i n g l e b i p o l a r electrode i n the amygdala of each subject. Each r a t was then stimulated twice a day f o r 16 consecutive days i n order to kindle motor seizures. At f i r s t , there was no response to each stimulation, but eventually mild motor seizures were e l i c i t e d and these increased i n s e v e r i t y u n t i l each stimulation r e l i a b l y e l i c i t e d a motor seizure characterized by a sequence of head clonus, rearing, forelimb clonus, and l o s s of equilibrium. The decrease i n the duration of the forelimb clonus component of the motor seizure was the measure used to gauge the anticonvulsive e f f e c t of alcohol. After s t a b l e baselines were established, the subjects i n one group were intubated with 4. 5 g/kg ethanol (303S solution) 90 min before, and an equivalent volume of s a l i n e 90 min after, each of f i v e b i d a i l y amygdaloid stimulations. The same substances were administered to the r a t s i n the c o n t r o l group but i n the reverse order. that i s . s a l i n e before each stimulation and 13 ethanol after. On the t e s t day, subjects i n both groups were in j e c t e d i n t r a p e r i t o n e a l l y with ethanol (1. 5 g/kg i n a 25% solution). The r a t s that had been stimulated while intoxicated during the tolerance development t r i a l s displayed more forelimb clonus than they had during pretesting that i s , they had become t o l e r a n t to the alcohol's anticonvulsant effect. In contrast, there was no diminution of alcohol's anticonvulsant action i n the al c o h o l - a f t e r — s t i m u l a t i o n animals. Tolerance that develops f o r a response only i f i t occurs during the period of drug exposure, such as that seen i n the P i n e l et a l . study has been termed "contingent tolerance. " This term was f i r s t coined by Carlton and Wolgin (1971), who observed that food-deprived r a t s who had been given eight i n j e c t i o n s of amphetamine each p r i o r to a period of food a v a i l a b i l i t y developed tolerance to amphetamine's anorexic effect, whereas those given eight i n j e c t i o n s of amphetamine each a f t e r a period of consumption d i d not. S i m i l a r r e s u l t s were reported by Chen (1968, 1972), who showed that s i g n i f i c a n t l e v e l s of tolerance developed f o r the d i s r u p t i v e e f f e c t s of alcohol on the performance of a c i r c u l a r maze i n only those subjects that had had an opportunity to p r a c t i c e the maze while intoxicated. He proposed that tolerance d i d not develop unless the subjects had an opportunity to learn motor and/or cognitive s t r a t e g i e s to counteract the d i s r u p t i v e e f f e c t s of the alcohol. E f f e c t i v e behaviours purportedly were learned because they increased the p r o b a b i l i t y of re c e i v i n g reinforcement while intoxicated. In h i s 1968 study. Chen employed the before-and-after design now r o u t i n e l y used i n many demonstrations of contingent tolerance. In Chen's version of the before-and-after design, subjects i n one group received the drug before each t e s t t r i a l 14 and s a l i n e a f t e r the test/ whereas subjects i n the other group received s a l i n e before the t r i a l and the drug afterwards. On the f i n a l t e s t day. a l l subjects received the drug p r i o r to the t e s t t r i a l . That there was more tolerance i n the drug-before—test subjects provided strong evidence f o r the importance of the response contingency i n the development of tolerance. Since Chen xs(1968. 1972) studies/ f i v e other examples of contingent alcohol tolerance have been reported. F i r s t , tolerance to the di s r u p t i v e e f f e c t s of alcohol on t r e a d m i l l running has been shown to develop more r a p i d l y when r a t s have had the opportunity to repeatedly practice the t r e a d m i l l task while i n t o x i c a t e d (LeBlanc. Gibbins. & Kalant. 1973; LeBlanc et al. , 1976i Mansfield. Benedict/ & Woods. 1983). Whether tolerance develops i n the a l c o h o l - a f t e r - t r e a d m i l l condition at a slower rate (LeBlanc et al. . 1976) or not at a l l (Wenger. Berlin. & Woods* 1980) has been a matter of debate. Second. Chen (1979) showed that on the t e s t day. r a t s given the opportunity to bar press f o r food reward during the tolerance a c q u i s i t i o n phase had shorter l a t e n c i e s to bar press than the co n t r o l subjects. given s a l i n e before the bar press task, during t h i s tolerance a c q u i s i t i o n period. Third. Traynor* Schlapler* and Barondes (1980) observed that tolerance to the alcohol-produced a c c e l e r a t i o n i n the decay of postsynaptic potentiation i n the abdominal ganglion of Aplysia occurred only when the presynaptic terminal was stimulated i n the presence of alcohol. Fourth* Alkana* Finn, and Malcolm <1983) and Hjeresen. Reed. Nakazono. and Woods (1983) reported that animals exposed to a warm environment a f t e r alcohol administration d i d not develop tolerance to a l c o h o l v s hypothermic e f f e c t unlike mice who were allowed to experience the f u l l hypothermic e f f e c t of alcohol administration. The 15 f i f t h and l a s t example mas the aforementioned study of tolerance to alcohol*s anticonvulsant e f f e c t (Pinel et al. » 1983). Although much of the research on contingent tolerance has involved alcohol, there have been several notable examples of contingent tolerance to other drugs. Rats that mere i n j e c t e d with d—amphetamine a f t e r access to milk did not develop as much tolerance to anorexic e f f e c t s of amphetamine* as those subjects given d-amphetamine and an opportunity to drink milk while drugged (Carlton & Wolgin* 1971* Demellweek & Goudie* 1983; Poulos et al. * 1981). Woolverton and Schuster (1978) reported that r a t s who had had an opportunity to drink milk while under the influence of cocaine developed greater tolerance to the anorexic e f f e c t s of cocaine than those subjects denied access to milk while intoxicated. Commissaris and Rech (1983) reported that r a t s given pentobarbital before being required to run on a r o t a t i n g rod developed greater tolerance to i t s d i s r u p t i v e e f f e c t s than those given pentobarbital a f t e r the task. Like Chen (1968)* most researchers have a t t r i b u t e d t h e i r demonstrations of contingent tolerance to idea that the animals learn coping or adapting s t r a t e g i e s that increase t h e i r chances of reinforcement* thereby* giving r i s e to the d i f f e r e n t i a l l e v e l of tolerance seen i n the animals given repeated opportunities to perform the task i n the drug state and i n those not given t h i s opportunity. This operant conditioning i n t e r p r e t a t i o n i s however not the only one put f o r t h as a possible explanation* a Pavlovian conditioning explanation has also been suggested. In fact* one does not need to appeal to a learning theory to explain many instances of contingent tolerance. A s t r e s s or habituation mechanism could r e a d i l y explain some instances of contingent tolerance. 16 However. researchers -typically o f f e r an operant learning explanation of contingent tolererance. Wenger et a l . (1980) suggested a Pavlovian i n t e r p r e t a t i o n of* contingent tolerance. Because the t e s t day f o r the saline-before-task subjects i s the f i r s t occasion on which they receive the drug before the task, the cues associated with t h i s drug administration are not the same as those associated with before and during the previous drug administrations. The Pavlovian view of learned tolerance would therefore p r e d i c t that one should not see as much tolerance i n the subjects who had received alcohol a f t e r the task than i n the subjects who received alcohol before the task (Wenger et al. * 1980). According to t h i s view, the presence of a t e s t before the i n j e c t i o n i s part of the CS and when the te s t i s not presented p r i o r to the i n j e c t i o n , there i s a resultant decline i n the magnitude of the conditioned compensatory response e l i c i t e d by the t e s t environment. Rationale Three experiments were conducted with the aim of f u l f i l l i n g one objective. The objective was to determine i f tolerance to the anticonvulsive e f f e c t of alcohol can develop i n the absence of Pavlovian conditioning. The r e s u l t s of the experiments would have two implications. One i s that by t e s t i n g a h i t h e r t o untested e f f e c t of alcohol i n the context of Siegel's model. the generality of the model would be extended or limited. The second i m p l i c a t i o n i s that these experiments are a te s t of the theory that contingent tolerance to alcohol's anticonvulsant e f f e c t can be viewed as a s p e c i a l instance of 17 Pavlovian conditioning. As j u s t outlined* t h i s claim a r i s e s •Prom the f a c t that on the t e s t day the a l c o h o l - a f t e r - t e s t subjects receive alcohol f o r the f i r s t time without i t being preceded by the test. Evidence f o r t h i s Pavlovian i n t e r p r e t a t i o n would be supplied by demonstrations that responses that are the subject of contingent tolerance can be brought under the c o n t r o l of environmental cues. Accordingly* the purpose of the present experiments was to determine whether Pavlovian conditioning i s necessary f o r the development of tolerance to a l c o h o l x s anticonvulsant effect. F a i l u r e to demonstrate environmental c o n t r o l of a l c o h o l % s anticonvulsant e f f e c t s under conditions comparable to those employed by P i n e l et a l . (1983) to demonstrate contingent tolerance would c o n s t i t u t e a d i r e c t challenge to the Pavlovian i n t e r p r e t a t i o n of contingent tolerance. General Methods Subjects The subjects i n each of the experiments were male hooded* 300-400g r a t s supplied by Charles River Canada housed s i n g l y with ad l i b i t u m access to standard laboratory chow and water. Surgery^ Xn each experiment* a s i n g l e b i p o l a r stimulation electrode was implanted i n the amygdala of each r a t 1. 2 mm pos t e r i o r to bregma. 5. 0 mm l e f t of the s a g g i t a l suture. and 9. 0 mm v e n t r a l to the dura of each rat. Tetracycline was sprinkled on the i n c i s i o n following surgery and added to the drinking water during the f i r s t 5 days of convalescence. 18 Kindlincj The k i n d l i n g phase of* each experiment, began a f t e r at l e a s t 5 days of p o s t s u r g i c a l recovery. Each r a t was stimulated ( 1 s. 400 «**.A r. m. s. . 60 Hz) three times per day. 5 days a week f o r 3 weeks. with at l e a s t 2 hr between consecutive stimulations. The experimenter removed each animal from i t s cage, placed i t i n a 58 x 58 x 25 cm opaque p l a s t i c chamber l i n e d with bedding. attached the leads, immediately stimulated i t . and returned i t to i t s home cage a f t e r the seizure. As expected (cf. Mucha & Pinel. 1977; P i n e l & Rovner. 1978). the r a t s at f i r s t did not respond to each stimulation. but by the l a s t of the 45 k i n d l i n g stimulations, most responded to each stimulation with a c l o n i c seizure characterized i n sequence by f a c i a l clonus. forelimb clonus, rearing. and a l o s s of equilibrium. The dependent va r i a b l e i n each experiment was the duration of the period of forelimb clonus. This measure has been shown to be s e n s i t i v e to experimental maninpulations designed to increase or decrease seizure s u s c e p t i b i l i t y < e. g. . Pinel. 1980. 1981 ). Baseline Following the k i n d l i n g phase of each experiment, each r a t was subjected to a s e r i e s of stimulations — hereafter r e f e r r e d to as baseline stimulations — to assess the s t a b i l i t y of i t s convulsive response to stimulation. Each subject was stimulated s i x times at 48-hr i n t e r v a l s . i n the chamber i n which i t was kindled, the f i r s t one occurring 48 hr a f t e r the l a s t of the 45 k i n d l i n g phase stimulations. Any subject that f a i l e d to display at l e a s t 10 s of forelimb clonus i n response to four of s i x baseline stimulations was excluded from the experiment at t h i s point. On one of the baseline days of Experiment 2. two experimenters independently 19 recorded a forelimb clonus duration score f o r each subject. A Pearson c o r r e l a t i o n c o e f f i c i e n t calculated f o r the paired scores, revealed high between-experimenter r e l i a b i l i t y , j^(56) = . 993, _p < . 001. Treatment Although the treatment phases of the experiments d i f f e r e d considerably, there were several features that were common to a l l of them. F i r s t , the 48-hr stimulation schedule i n i t i a t e d during the s t a b i l i z a t i o n phase was maintained u n t i l the end of the experiment. Accordingly, the treatment phase of a l l experiments began 48 hr a f t e r the l a s t baseline stimulation. On each treatment day, each subject received an i n t r a p e r i t o n e a l i n j e c t i o n of ei t h e r 1. 5 g/kg ethanol (25/i solution) or an equivalent volume of s a l i n e (7. 6 ml/kg) 60 min before the stimulation. The drug administration procedure, employed on each of the treatment days was as follows. Each animal was removed from i t s home cage, weighed and then placed i n the treatment chamber 5 min p r i o r to re c e i v i n g the inj e c t i o n . After r e c e i v i n g the i n j e c t i o n , each r a t was returned to the same chamber f o r 1 hr before r e c e i v i n g an amygdaloid stimulation and being returned to i t s home cage 5 min later. In experiments i n v o l v i n g more than one treatment chamber, treatment environments were counterbalanced to negate any nonassociative e f f e c t s that might inadvertantly a f f e c t the results. For example i n Experiment 1, Environment A was the alc o h o l - p r e d i c t i v e environment f o r h a l f of the animals and Environment B, f o r the other half. Blood Samples A t a i l blood sample was taken from each subject on the f i r s t day of alco h o l administration and on the t e s t day, j u s t 20 be-Fore i t was returned to i t s home cage. In order to obtain blood samples, each r a t was restrained i n a c y l i n d r i c a l cardboard tube, the t a i l was brie-fly immersed i n warm water to increase blood flow. After the t i p of the t a i l of each r a t was snipped. blood was c o l l e c t e d i n a heparinized micropipette. which was immediately sealed. l a b e l l e d . and stored i n a freezer. Test During the t e s t session 48 hr a f t e r the l a s t treatment stimulation, each r a t was in j e c t e d with ethanol (1. 5 g/kg of a 25% solution) 1 hr p r i o r to an amygdaloid stimulation. In Experiments 1 and 2. the e f f e c t of manipulations on tolerance to the anticonvulsive e f f e c t of alcohol was of interest. Consequently, only subjects judged to have developed tolerance were included i n subsequent tests. A subject was considered to have developed tolerance to the anticonvulsive e f f e c t of alcohol i f i t s forelimb clonus duration on the f i r s t day of alcohol administration was l e s s than the mean of i t s clonus durations on the l a s t three alcohol sessions of the tolerance development phase. In Experiment 3, however. a l l subjects that achieved the baseline c r i t e r i o n were included i n a l l of the subsequent phases of the experiment. In Experiment 3. the e f f e c t of CS preexposure on the development of tolerance was of interest. Accordingly. i t was e s s e n t i a l to include a l l subjects i n the analyses regardless of the l e v e l of tolerance achieved. Histology At the end of the experiments, a l l animals were k i l l e d i n a C0^_ chamber, according to Canada Council on Animal Care guidelines, and t h e i r brains were removed and stained using 21 the blue-dot s t a i n i n g technique (Skinner* 1971) i n order to F a c i l i t a t e h i s t o l o g i c a l confirmation of the electrode s i t e . A fter each rat was perfused with a saturated potassium ferrocyanide formaldehyde solution* a d i r e c t current was passed through the electrode* d r i v i n g i r o n ions i n t o the t i s s u e surrounding the electrode t i p . These ions turn a dark blue i n the presence of the potassium ferrocyanide* thus revealing the p o s i t i o n of the electrode t i p . Blood Alcohol Analysis Blood alcohol l e v e l s were determined by the gas chromatograph technique of Gibbins* Kalant* and LeBlanc (1968) and Wallgren and Barry ( 1970). In t h i s technique* each blood sample was dissolved i n propanol before being heated to approximately 63 C f o r 3 min. The gas from the heated blood-propanol s o l u t i o n was then i n j e c t e d i n t o the gas chromatograph to allow mixing with the nitrogen gas carrier. The column used to f i l t e r the gas sample was graphitised carbon black coated with a Q. 2V. carbowax coating. The proportion of e t h y l alcohol i n the blood sample r e l a t i v e to that of the propanol was graphed on a recorder allowing f o r subsequent comparisons with standards i n order to determine alcohol concentration. S t a t i s t i c a l Analysis Gross v i o l a t i o n s i n the assumption of homogeneity of variance necessitated the use of l e s s powerful nonparametric procedures i n the s t a t i s t i c a l a n a l ysis of the r e s u l t s of each experiment. To evaluate the s t a b i l i t y of the baselines i n each experiment* the s i g n i f i c a n c e of differences i n the duration of forelimb clonus between the l a s t three baseline days was assessed with Friedman"s nonparametric two-way 22 analysis of* variance f o r re l a t e d samples (Siegel/ 1956). The Wilcoxon Matched-Pairs Signed-Ranks Test (Siegel, 1956) and the Mann-Whitney jJ. Test (Siegel, 1956) were used to make i n d i v i d u a l a p r i o r i comparisons between and within groups, respectively. Multiple comparisons of course increase the alpha l e v e l , but they also lead to greater power. This makes i t more l i k e l y to f a l s e l y r e j e c t the n u l l hypothesis, and l e s s l i k e l y to accept i t . Accordingly, i n cases i n which we accepted the n u l l hypothesis, our conclusions were a l l the more credible. The l e v e l of s i g n i f i c a n c e employed f o r a l l s t a t i s t i c a l comparisons was . 05, however the actual p r o b a b i l i t y of each diff e r e n c e (within the l i m i t s of the a v a i l a b l e tables) was reported i n the text. Experiment 1 One purpose of Experiment 1 was to determine whether tolerance to the anticonvulsive e f f e c t of alcohol i s subject to environmental control, that i s , whether or not subjects display more tolerance to the anticonvulsive e f f e c t of alcohol i f alcohol i s administered i n an a l c o h o l — p r e d i c t i v e environment than i f i t i s administered i n a s a l i n e - p r e d i c t i v e environment. The second purpose was to determine whether or not a compensatory conditioned response would be e l i c i t e d i n subjects t o l e r a n t to alcohol's anticonvulsant effect, that i s , whether or not an i n j e c t i o n of s a l i n e administered i n an a l c o h o l - p r e d i c t i v e environment would increase the duration of forelimb clonus e l i c i t e d by subsequent convulsive stimulation. Methods 23 Subjects. Of the 60 rats that began the experiment* 4 died of p o s t s u r g i c a l complications. 2 mere excluded a f t e r t h e i r electrodes mere rejected. 2 did not reach the c r i t e r i o n of baseline s t a b i l i t y , i . e. at l e a s t 10 s of forelimb clonus on at l e a s t four of the six baseline stimulations, and 9 died during the treatment phase. leaving a t o t a l of 43 that completed the treatment phase of the experiment. Treatment. Following k i n d l i n g and baseline testing, a l l subjects meeting the c r i t e r i o n of s t a b i l i t y were i n j e c t e d and stimulated on alterna t e days. i n one of two d i s t i n c t i v e environments. A or B. Environment A was an 58 x 58 x 25 cm opaque, p l a s t i c chamber, l i n e d with almond-scented shredded paper. This chamber. situated i n a room upstairs from the colony room was illuminated by both natural and a r t i f i c i a l l i g h t . The colony room housed chamber B. which was a chamber s i m i l a r to the one described above, however i t was l i n e d with an unscented corn cob bedding material, and was illuminated e n t i r e l y by a r t i f i c a l l i g h t only. D i f f e r e n t experimenters were responsible f o r the t e s t i n g i n each of the two environments. On the f i r s t treatment day. a l l subjects were i n j e c t e d with e i t h e r alcohol or s a l i n e and stimulated i n environment A. Subjects were removed from t h e i r home cages by Experimenter A. placed i n groups of f i v e or s ix i n a carrying cage, and transported to t e s t chamber A. where each subject remained i n the ca r r y i n g cage f o r 5 to 20 min. After being placed i n the t e s t chamber f o r 5 min. each subject received an i n t r a p e r i t o n e a l i n j e c t i o n of e i t h e r alcohol (1. 5 g/kg of a 25% solution) or an equivalent volume of s a l i n e (7. 6 ml/kg). Immediately a f t e r the i n j e c t i o n , each subject was returned to the t e s t chamber f o r 1 hr there before having i t s leads 24 attached and being stimulated. Each subject mas removed From the t e s t chamber 5 min a f t e r stimulation, placed i n a carryi n g cage with f i v e or six other subjects, and returned to i t s home cage. On the second treatment day, 48 hr lat e r , a l l subjects were removed from t h e i r home cages, placed i n carrying cages i n groups of f i v e or six by Experimenter 8 and transported to te s t chamber B. As before, each subject remained i n the carrying cage f o r 5 to 20 min, before being placed i n the t e s t chamber, i n j e c t e d 5 min lat e r , and stimulated 1 hr a f t e r that. Once again, each animal was removed from the t e s t chamber 5 min a f t e r stimulation, placed i n a carrying cage with f i v e or six other rats, and returned to i t s home cage. Those subjects that had received alcohol on the f i r s t day received s a l i n e on the second and vic e versa. There were a t o t a l of 10 treatment days such that days 3, 5, 7, 9 were i d e n t i c a l to day 1 and days 2, 4, 6, 8 were i d e n t i c a l to day 2. Thus, each subject received 10 injections, 5 alc o h o l i n j e c t i o n s i n the a l c o h o l - p r e d i c t i v e environment and 5 s a l i n e i n j e c t i o n s i n the s a l i n e - p r e d i c t i v e environment. Alcohol Test Day. On the alcohol t e s t day , each subject received a l c o h o l i n one of the two te s t environments. Those subjects r e c e i v i n g alcohol i n the environment i n which they had previously received alcohol comprised the Same Group, whereas those r e c e i v i n g alcohol i n t h e i r s a l i n e - p r e d i c t i v e environment comprised the D i f f e r e n t Group. Subjects were divided i n t o the two groups p r i o r to t e s t i n g such that t h e i r mean forelimb clonus durations on the f i f t h alcohol session were approximately the same f o r both groups and such that h a l f of the subjects i n each group received t h e i r alcohol t e s t 25 i n j e c t i o n i n each of the two t e s t environments. A l l subjects received the t e s t i n j e c t i o n i n accordance with the drug administration procedures used during the treatment t r i a l s . S aline Test Day. Only those subjects that had received t h e i r alcohol t e s t i n j e c t i o n s i n the a l c o h o l - p r e d i c t i v e environment p a r t i c i p a t e d i n the s a l i n e t e s t 48 hr later. These subjects were i n j e c t e d with s a l i n e i n the alc o h o l - p r e d i c t i v e environment (Environment A f o r h a l f the rats and 8 f o r the others) 1 hr p r i o r to stimulation. Results The r e s u l t s of Experiment 1 confirm the previous report of P i n e l et al. <1983) that tolerance develops r a p i d l y to alcohol*s anticonvulsive e f f e c t on kindled seizures. The mean duration of forelimb clonus e l i c i t e d i n the 43 subjects on the f i r s t a l cohol t r i a l was only 3. 09 s. and i t had increased to 14. 40 s by the f i f t h and l a s t tolerance development t r i a l . X<43)= 5. j> < . 002. Because the purpose of the present study was to i d e n t i f y f a c t o r s that influence the development of tolerance. only those subjects that had displayed some evidence of tolerance were included i n the t e s t phases of the experiment — 10 subjects whose mean clonus durations on the l a s t three alcohol t r i a l s of the treatment phase were not higher than t h e i r clonus durations on the f i r s t alcohol session were not tested. Thus, completing the experiment were 33 subjects. 17 i n the Di f f e r e n t Group and 16 i n the Same Group. The data of these subjects are presented i n Figure 1. which i l l u s t r a t e s the major f i n d i n g s of t h i s study. Baseline. I t i s c l e a r from Figure 1 that stable 26 baselines were achieved by the end of the baseline period. There was no s i g n i f i c a n t change i n duration of forelimb clonus over the l a s t 3 baseline days i n ei t h e r the D i f f e r e n t Group, XY-(2, N=17)= 1. 88, _p > . 30 or the Same Group, A~c (2, N=16) = 1. 20, p > . 50, and the groups did not d i f f e r s i g n i f i c a n t l y on any of these 3 days, ( a l l three Mann-Whitney UJs > 121, a l l _p ss > .10). Treatment. During the treatment phase, a l l subjects received 10 stimulations, f i v e following s a l i n e i n j e c t i o n s and f i v e following alcohol i n j e c t i o n s on alternat e days. A comparison of the duration of the forelimb clonus e l i c i t e d on the f i v e s a l i n e t r i a l s with the clonus durations of the baseline phase (see Figure 1) established that the i n j e c t i o n procedure per se d i d not a f f e c t the duration of forelimb clonus. The addition of a s a l i n e i n j e c t i o n 60 min before the convulsive stimulation had no s i g n i f i c a n t e f f e c t i comparisons of the clonus e l i c i t e d on the l a s t baseline day and the l a s t s a l i n e treatment day, both probably r e l e c t i n g the most stable performance f o r that phase revealed no s i g n i f i c a n t change i n either the D i f f e r e n t Group, _T(17) = 52.0, p > .13, or the Same Group, JT(16)= 44. 0, _p > . 12. Moreover there was no s i g n i f i c a n t s h i f t i n the baselines of e i t h e r group over the treatment days. Comparisons of the durations on the f i r s t s a l i n e treatment day with those on the l a s t s a l i n e treatment day revealed no s i g n i f i c a n t d i f ferences f o r the D i f f e r e n t Group, T(17)= 46. 0, _p > . 10 and Same Group, J_(16)= 42. 0, p > . 10, subjects. Also, both groups of subjects exhibited v i r t u a l l y equivalent clonus durations on each of the s a l i n e treatment days ( a l l f i v e Mann-Whitney U_'s > 140, a l l _p xs > . 40). The performance of the subjects on the f i v e alcohol 27 Figure 1. The effect- of s a l i n e or alcohol i n j e c t i o n s on the duration of forelimb clonus e l i c i t e d i n kindled ra t s by amygdaloid stimulation. Following 6 baseline days, the subjects i n two groups received alcohol i n j e c t i o n s p r i o r to odd numbered stimula-t i o n s and s a l i n e i n a d i s t i n c t i v e l y d i f f e r e n t en-vironment p r i o r to even number stimulations. During the alcohol test, the subjects i n the Same Group r e -ceived the alcohol and t e s t stimulation i n the same environment i n which they had previously received i t . whereas those i n the D i f f e r e n t Group received the alcohol and t e s t stimulation i n the environment i n which they had previously received saline. On the s a l i n e test, the subjects i n the Same Group received a s a l i n e i n j e c t i o n i n the environment i n which they had always received alcohol. Stimu-l a t i o n s were administered at 48 hr i n t e r v a l s throughout the experiment. The s o l i d l i n e s repre-sent the performance of the D i f f e r e n t Group subjects whereas the dashed l i n e s represent, that of the Same Group subjects. The symbols i n d i c a t e which treatment the subjects received before stimulation. The diamonds, squares, and c i r c l e s i n d i c a t e that no treatment, alcohol i n j e c t i o n s or s a l i n e i n j e c t i o n s , r e s p e c t i v e l y were given p r i o r to stimulation. 2 8 4 0 -u 3 5 -C O C/3 30 -O < 2 5 -a CO 2 0 -O u 1 5 -CD L U 1 0 -CC o LL. 5-saline sessions SAME DIFFERENT alcohol sessions i — r i r — i — i — i — i — i — i 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 1 2 LBaselineJ ' — T r e a t m e n t — 1 LTest^ STIMULATIONS 29 t r i a l s i s noteworthy i n two respects. The f i r s t i s that there was a s u b s t a n t i a l decrease i n the anticonvulsive e f f e c t of alcohol over the f i v e t r i a l s f o r each of the two groups* X<17)= 0 and T(16)= 0, b o t h j ^ s < .002. The second* i s that the groups did not d i f f e r s i g n i f i c a n t l y on any of the f i v e t r i a l s * ( a l l f i v e Mann-Whitney U/s > 23. a l l p > .10). Alcohol Test. On the alcohol test* both groups were in j e c t e d with alcohol, those i n the Same Croup were i n j e c t e d and stimulated i n the al c o h o l - p r e d i c t i v e environment* whereas those i n the D i f f e r e n t Group subjects were in j e c t e d and stimulated i n the s a l i n e - p r e d i c t i v e environment. Both groups displayed c l e a r tolerance ; i n contrast to the f i r s t alcohol i n j e c t i o n * the f i f t h alcohol i n j e c t i o n produced s u b s t a n t i a l l y more forelimb clonus i n both the Di f f e r e n t Group* JT(17) = 5* p < . 004 and the Same Group* J_(16) = 0* p < . 0002. However, i t i s c l e a r i n Figure 1 that the i n j e c t i o n environment had no e f f e c t on the duration of forelimb clonus. There was no s i g n i f i c a n t d i f f e r e n c e between the two groups i n the duration of the forelimb clonus elicited., on the alcohol t e s t day* JJ(16, 17)= 133* p > . 10. Saline Test. I n j e c t i o n of s a l i n e i n the alc o h o l - p r e d i c t i v e environment did not e l i c i t the increase i n forelimb clonus duration predicted by S i e g e l x s theory. The seizures e l i c i t e d i n the subjects of the Same Group on the sa l i n e t e s t were not s i g n i f i c a n t l y longer than those e l i c i t e d following s a l i n e i n j e c t i o n s i n the s a l i n e - p r e d i c t i v e environment during the treatment phase of the experiment. For example* seizures seen on the s a l i n e t e s t day were not s i g n i f i c a n t l y longer than those on the l a s t s a l i n e treatment day, T^db)^ 53, £ > . 23. In fact* there was a small but 30 in s i g n i f i c a n t , decline i n duration on the s a l i n e t e s t day. Dissussion [ The two major fin d i n g s of the present experiment are c l e a r l y at odds with Siegel^s Pavlovian i n t e r p r e t a t i o n of drug tolerance. F i r s t / tolerance to the anticonvulsive e f f e c t of alcohol was not found to be under environmental control. Animals that had received alcohol i n one environment and s a l i n e i n another during the treatment phase displayed the same degree of tolerance to the anticonvulsive e f f e c t of alcohol regardless of which of the two environments the t e s t i n j e c t i o n was administered. Second/ there was no evidence that environmental cues repeatedly paired with the anticonvulsant e f f e c t s of alcohol e l i c i t a conditioned compensatory reponse. An i n j e c t i o n of s a l i n e i n the al c o h o l - p r e d i c t i v e environment did not s i g n i f i c a n t l y increase the forelimb clonus duration e l i c i t e d i n kindled r a t s by amygdaloid stimulation — i n fact/ a small decrease was observed. These two fi n d i n g s contrast with previous reports of Crowell et al. (1981)/ Le et al. (1979) and Mansfield and Cunningham (1980) i n which conditioned compensatory responses as well as s i t u a t i o n a l s p e c i f i c i t y were demonstrated i n r a t s t o l e r a n t to the hypothermic e f f e c t of alcohol. One possible reason f o r t h i s d i f f e r e n c e i n r e s u l t s may be that the development of tolerance to only some of the e f f e c t s of alcohol i s dependent on Pavlovian mechanisms. Supporting t h i s view i s that methods of the present experiments unrelated to the measurement of seizure duration were generally comparable to those of the studies supporting the Pavlovian view of alcohol tolerance. Of course/ other explanations are possible. For example/ the i n j e c t i o n environment may have had 31 no obvious effect, i n Experiment. 1 because the alcohol and s a l i n e environments may not have been s u f f i c i e n t l y discriminable. However, i n view of the i n j e c t i o n environments used s u c c e s s f u l l y i n the e a r l i e r studies, those used i n Experiment 1 should have been r e a d i l y discriminable to the subjects — they d i f f e r e d with respect to smell, t e s t i n g chamber, room, l i g h t , and experimenter. Another p o s s i b i l i t y i s that the 10 t r i a l s used i n the treatment phase have not been enough f o r the c o n t r o l l i n g e f f e c t s of the i n j e c t i o n environment to be realized. Other researchers have used as few as 4 (Melchior & Tabakoff, 1981) or as many as 20 (Crowell et a l . , 1981) alcohol t r i a l s i n t h e i r studies. The important point i s , however, that a marked tolerance e f f e c t did develop during the course of the present experiments, and according to Siegel"s theory, so should have any conditioning. Experiment 2 I f a p a r t i c u l a r manifestation of alcohol tolerance were the r e s u l t of Pavlovian conditioning, then i t would be possible to accelerate the d i s s i p a t i o n of tolerance by employing e x t i n c t i o n procedures. Tolerant subjects repeatedly exposed to the CS without the UCS should display l e s s tolerance than t o l e r a n t subjects not given the e x t i n c t i o n t r i a l s . The purpose of Experiment 2 was to determine i f tolerance to the anticonvulsant e f f e c t of alcohol can be extinguished. Methods Subjects. Of the 29 subjects that started Experiment 2, 32 4 died during the course of the experiment and 1 did not achieve the c r i t e r i o n of at l e a s t 10 s of forelimb clonus on 4 of the 6 baseline days. Accordingly, a t o t a l of 24 r a t s completed the tolerance development phase of the experiment. Baseline. As i n Experiment 1, each subject received s i x baseline stimulations, one every 48 hr, thus i n i t i a t i n g a b i d a i l y stimulation regimen that was maintained u n t i l the end of the experiment. A l l baseline stimulations were administered by Experimenter A (see Experiment 1). Tolerance Development. Each subject underwent the f i r s t of f i v e tolerance development sessions i d e n t i c a l to those administered i n Experiment 1, 48 hr a f t e r the l a s t baseline stimulation. A l l tolerance development t r i a l s were administered i n environment A by Experimenter A (see Experiment 1). Extinction. Following the tolerance development phase of the experiment, the subjects were assigned to one of two groups an E x t i n c t i o n Group or a Control Group, such that both groups had comparable duration scores. Accordingly, p r i o r to each of the f i v e b i d a i l y stimulations comprising the e x t i n c t i o n phase, each subject received e i t h e r an e x t i n c t i o n t r i a l or a c o n t r o l t r i a l . On each e x t i n c t i o n t r i a l , Experimenter A i n j e c t e d and stimulated each subject i n environment A as she had done on the tolerance—development days except that s a l i n e (7. 6 ml/kg) rather than ethanol was administered. During the e x t i n c t i o n phase, the c o n t r o l subjects received f i v e b i d a i l y stimulations from Experimenter B i n environment B. 33 Test Day. A l l subjects received a t e s t i n j e c t i o n i n Environment A, 48 hr a f t e r the f i f t h and f i n a l e x t i n c t i o n or co n t r o l t r i a l . The i n j e c t i o n and stimulation procedure used on the t e s t day mas i d e n t i c a l to that used on each of the tolerance development sessions. Results In Experiment 2 as i n Experiment 1, subjects developed s u b s t a n t i a l tolerance to a l c o h o l x s anticonvulsive e f f e c t over the f i v e tolerance development injections. The mean forelimb clonus duration on the f i r s t tolerance development day f o r a l l subjects was 6. 97 s» whereas on the l a s t tolerance development day. the mean was 44. 50 s. X<24)= 15/ < . 0002. Once again/ only those subjects d i s p l a y i n g a forelimb clonus duration on the f i r s t tolerance development day smaller than the mean of the durations on the l a s t 3 tolerance development days were included i n subsequent phases of the experiment. Of the 24 subjects that underwent the tolerance development phase/ 22 achieved t h i s c r i t e r i o n . I t was the scores of these 22 subjects/ 11 i n the E x t i n c t i o n Group and 11 i n the Control Group/ that were subjected to s t a t i s t i c a l a nalysis and gr a p h i c a l l y represented i n Figure 2. Baseline. By the end of the baseline phase/ the durations of forelimb clonus were stable. Not only were there no s i g n i f i c a n t d i f f e r e n c e s between the two groups on any of the l a s t three baseline sessions ( a l l three Mann-Whitney ITs > 51/ a l l p**s > .10)/ but the scores of neither the Ext i n c t i o n A* (2/ N=ll)= 5. 5/ p > . 55 nor the Control Ar(2/ N=ll)= . 55/ p > . 70 subjects varied s i g n i f i c a n t l y over these 3 baseline days. 34 Figure 2. The e f f e c t of e x t i n c t i o n procedures on the duration of Forelimb clonus e l i c i t e d i n kindled r a t s by amygdaloid stimulation. After the subjects devel-oped tolerance to the anticonvulsant e f f e c t s of alcohol one group of subjects received s a l i n e i n -j e c t i o n s before stimulation i n the environment that previously predicted alcohol administration while another group of subjects received the stimulation only i n an environment that was not associated with al c o h o l administration. On the t e s t day. a l l subjects received alcohol i n the a l c o h o l - p r e d i c t i v e environment p r i o r to being stimulated. Stimulations were administered at 48 hr i n t e r v a l s . The s o l i d l i n e s represent the performance of the E x t i n c t i o n Group subjects whereas the dashed l i n e s represent that of the Control Group subjects. The symbols i n -cate which treatment the subjects received before stimulation. The diamonds, squares and c i r c l e s i n -cate that no treatment, alcohol i n j e c t i o n s or s a l i n e i n j e c t i o n s , r e s p e c t i v e l y were given p r i o r to s t i m u l -ation. Although, the Control Group subjects did not receive s a l i n e during the e x t i n c t i o n phase, t h e i r performance during the e x t i n c t i o n phase i s repre-sented by c i r c l e s f o r c l a r i t y . 35 52-o 48-44-40-o r— 36-< 32-O 00 28-ZD 24-o 20-16-_ l LU 12-QC o LU 8-4-baseline sessions extinction sessions EXTINCTION CONTROL alcohol sessions i r —I—i— I— I— i—I— I— l— I— I— I 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 | L Basel ine- 1 L Tolerance J L E x t i n c t i o n J T e s t Development STIMULATIONS 36 Tolerance Development,. As indicated by Figure 2, both groups of subjects displayed s i m i l a r patterns of tolerance development. For example. subjects i n the E x t i n c t i o n Group did not d i f f e r s i g n i f i c a n t l y from those i n the Control Group on e i t h e r the f i r s t * JJ<3, 1) = 2, _p_ > .75 or l a s t , U_(ll, 11)= 50, p > . 10 tolerance development day. Extinction. On each of the f i v e e x t i n c t i o n t r i a l s , the subjects showed s i m i l a r l e v e l s of forelimb clonus regardless of the environment i n which the e x t i n c t i o n treatments were given. The two groups of subjects did not d i f f e r s i g n i f i c a n t l y from each other on the f i r s t e x t i n c t i o n day, U<11, 11)= 57, _p > . 10, or the la s t , L K l l , 11)= 63, _E > • 10 respectively. In addition, each group of subjects showed no s i g n i f i c a n t changes i n forelimb clonus duration as a r e s u l t of the repeated e x t i n c t i o n t r i a l s , that i s , between the f i r s t and l a s t e x t i n c t i o n days, both T % s > 24, p*s > . 46. Test Day. Contrary to the predictions made from Siegel^s Pavlovian model of tolerance, the two groups were not s i g n i f i c a n t l y d i f f e r e n t from each other on the t e s t t r i a l , _y_(l, 3)= 1, _g > . 25. Neither group displayed any evidence of tolerance on the t e s t day ; neither the forelimb clonus durations of the E x t i n c t i o n Group, X*4)= 1, _p > . 12 nor the Control Group, _T(4)= 2, jp > . 13 were any longer than t h e i r respective l e v e l s on the f i r s t tolerance development day. Discussion Tolerant animals, having undergone e x t i n c t i o n t r i a l s did not d i f f e r from t o l e r a n t r a t s that had not received the e x t i n c t i o n procedure; tolerance dissipated completely i n both groups between the end of the tolerance development phase and 37 the t e s t day. In looking at Figure 2, i t i s obvious that on the t e s t day, the e x t i n c t i o n group and co n t r o l group subjects mere so close to zero, that had there been a s i g n i f i c a n t l y d i f f e r e n t i a l l e v e l of forelimb clonus between the groups, i t would not have been possible to observe i t . That e x t i n c t i o n of tolerance to the anticonvulsive e f f e c t of alcohol was demonstrated i s c l e a r l y i n doubt. However, the rapid d i s s i p a t i o n of tolerance i n the subjects not having undergone ex t i n c t i o n t r i a l s i s at odds with the findings reported by three independent laboratories. Crowell et al. (1981), Le et al. (1979) and Mansfield and Cunningham (1980) have a l l reported attenuation of tolerance to the hypothermic e f f e c t of alcohol i n only those t o l e r a n t subjects that had been exposed to the environmental cues (CS) without the drug (UCS), during the e x t i n c t i o n phase. In each of these studies, a f t e r the period of tolerance acqu i s i t i o n , one group of subjects was given s a l i n e i n the presence of alcohol-associated cues, while the other group was l e f t i n the home cage, r e l a t i v e l y undisturbed, or given s a l i n e i n the presence of saline-associated cues. The marked decrease of forelimb clonus i n the co n t r o l group contrary to the p r e d i c t i o n made from Siegel's model suggest that there was no conditioning underlying the development of tolerance to the anticonvulsive e f f e c t of alcohol. Experiment 3 The purpose of Experiment 3 was to determine whether CS preexposure, a treatment that has a major e f f e c t on Pavlovian conditioning would influence the development of tolerance to alcohol's anticonvulsant effects. Would repeated exposure to 38 the a l c o h o l - p r e d i c t i v e cues without the a l c o h o l retard subsequent development of tolerance to alcohol's anticonvulsant e f f e c t s ? Although tolerance to morphine's analgesic e f f e c t has been subjected to such a manipulation (Bardo 3c Hughes, 1979. Sherman, Proctor, & Strub, 1982), i t has never been applied to any example of alcohol tolerance. Methods Subjects. Of the 30 subjects that started t h i s experiment, 1 subject was eliminated a f t e r the baseline phase due to an i r r e p a r a b l y clogged electrode, and 4 subjects died. Accordingly, 25 r a t s completed the tolerance development phase of the experiment. Baseline. The baseline phase of the experiment was i d e n t i c a l to that of Experiments 1 and 2. A l l 30 subjects that s t a r t e d the experiment met the c r i t e r i o n of baseline s t a b i l i t y . Preexposure. After the six b i d a i l y baseline stimulations, subjects were assigned to one of two groups, which received e i t h e r a CS preexposure treatment (Preexposure Group, n=13) or a c o n t r o l treatment (Control Group, n=12) p r i o r to each of the succeeding f i v e stimulations. The preexposure subjects were i n j e c t e d and stimulated by Experimenter A using the drug administration procedure described e a r l i e r except of course, that s a l i n e (7.6 ml/kg) rather than alcohol was i n j e c t e d i n Environment A. Each subject was placed i n the t e s t chamber, i n j e c t e d 5 min later, stimulated 1 hr afterwards and was removed from the t e s t chamber 5 min a f t e r stimulation. Accordingly, the Preexposure 39 subjects were preexposed to a l l of the cues that subsequently predicted the administration of alcohol. The Control Group subjects were also i n j e c t e d with s a l i n e and stimulated during the preexposure phase but by Experimenter B and i n Environment B — a treatment i d e n t i c a l to that given to the E x t i n c t i o n Group subjects during the e x t i n c t i o n phase of Experiment 2. Tolerance Development and Test. A f t e r the f i v e preexposure or c o n t r o l t r i a l s , a l l subjects were i n j e c t e d i n t r a p e r i t o n e a l l y with alcohol ( 1. 5 g/kg of a 25% solution) i n Environment A, 1 hr p r i o r to each of the next s i x stimulations according to the drug administration procedure used i n Experiment 1 and 2. The s i x t h session constituted the t e s t t r i a l . Results Preexposure to the cues that would subsequently be associated with alcohol administration did not attenuate the rate of tolerance development. The mean l e v e l of seizure a c t i v i t y exhibited by the Preexposure and Control Group subjects during the baseline, preexposure, tolerance development, and t e s t phases of the experiment i s shown i n Figure 3. Baseline. Subjects i n both the Preexposure Group (n=13) and the Control Group (n=12) displayed stable l e v e l s of forelimb clonus by the end of the baseline pha^se. The Preexposure, A*~(2, N=13)= 3.9, j> > . 10 and Control, (2, N=12) = 0. 5, _p > . 70, Groups showed stable l e v e l s of forelimb clonus by the l a s t three baseline days. In addition, the two groups did not d i f f e r s i g n i f i c a n t l y from each other on any of these 3 days ( a l l three Mann-Whitney IPs > 50, a l l p's > .10). 40 Figure 3. The effect, of preexposing subjects to the CS only, before CS-UCS pairing, on the duration of forelimb clonus e l i c i t e d by an amygdaloid stimulation i n Kindled rats. In the preexposure phase, subjects i n the Preexposure Group were given s a l i n e i n the environment that would sub-sequently p r e d i c t alcohol administration, while Control Group subjects were given s a l i n e i n the environment that would not subsequently be assoc-i a t e d with alcohol. During the tolerance develop-ment sessions and on the t e s t session, a l l subjects received alcohol i n the alcohol-cued environment p r i o r to r e c e i v i n g amygdaloid stimulation. The stimulations were given at 48 hr i n t e r v a l s . The s o l i d l i n e s represent the performance of the Pre-exposure Group subjects whereas the dashed l i n e s represent that of the Control Group subjects. The symbols in d i c a t e which treatment the subjects received p r i o r to stimulation. The diamonds, c i r -c l e s and squares i n d i c a t e that no treatment, s a l i n e i n j e c t i o n s or alcohol injections, r e s p e c t i v e l y were given p r i o r to stimulation. STIMULATIONS 42 Preexposure. Control Group subjects did not d i f f e r s i g n i f i c a n t l y from the Preexposure Group subjects on any of the f i v e preexposure sessions ( a l l f i v e Mann-Whitney JJ_" s > 58, a l l _ p " s > .10). Repeated sessions did not s i g n i f i c a n t l y a l t e r the l e v e l s of forelimb clonus exhibited by the Preexposure Xy(4. N=13)= 3.4, £ > . 30 and Control, Xj- (4, N=12)= 4.3, p > . 30, subjects during the preexposure phase. Tolerance Development and Test Day. On the f i r s t tolerance development day, alcohol administration completely blocked seizures i n a l l subjects, but by the t e s t day, both the Preexposure group, J_(13)= 3, £ <. 0002 and Control group, T(12)= 3, j> < . 0004, subjects exhibited considerable tolerance. The two groups of subjects did not d i f f e r s i g n i f c a n t l y on the t e s t day, _U(10» 11)= 67, £ > . 10. Discussion Contrary to the p r e d i c t i o n based on S i e g e l % s theory (1977), experience with the cues that would l a t e r s i g n a l alcohol administration did not a l t e r the rate of tolerance development or the f i n a l l e v e l of tolerance to the anticonvulsive e f f e c t of alcohol. In fact, both groups of subjects demonstrated comparable l e v e l s of seizure a c t i v i t y throughout the preexposure tolerance development, and t e s t phases. Clearly, the p r e d i c t i o n from 5 i e g e l v s Pavlovian theory that CS preexposure would retard the development of tolerance has not been confirmed. As discussed e a r l i e r , there have been very few reports assessing the e f f e c t of CS preexposure on tolerance. Thus, although the e f f e c t s of CS preexposure suggests that Pavlovian conditioning may underlie some manifestations of drug tolerance, the f a i l u r e of CS preexposure to retard tolerance i n the present experiment 43 argues against the r o l e of Pavlovian conditioning i n the development of tolerance to a l c o h o l % s anticonvulsive effect. Histology and Blood Alcohol Analysis Blood alcohol concentrations between groups and between days, i n each experiment were analyzed by a repeated measures ANOVA. In Experiments 1, 2, and 3, differences i n blood alcohol l e v e l s between the D i f f e r e n t and Same Group subjects, F<1, 30) = . 56, £ > . 25, the Ex t i n c t i o n and Control Group subjects, Jz(l, 20)= 1. 62, £ > . 22, and the Preexposure and Control Group subjects, _F(1, 22) = . 027, p > . 25 were not found to be s i g n i f i c a n t . In addition, no s i g n i f i c a n t d i f f e r e n c e s across days due to metabolic accumulation of alcohol were seen i n Experiment 1, _F<1, 30) = . 07, _p > . 25, Experiment 2, £(1, 20) = . 98, p > . 34, or Experiment 3, JF(1, 22)= 1. 97, _p > . 10. The actual blood alcohol l e v e l s f o r each sample taken from each group f o r a l l three experiments are presented i n Table 2. Figures 4, 5, and 6 show the stimulation s i t e s i n the brains of subjects i n Experiments 1, 2, and 3, respectively. Most of the electrode t i p s were situat e d i n the r i g h t medial, l a t e r a l , b a s o l a t e r a l and c o r t i c a l amygdaloid nuclei. The most a n t e r i o r a l l y placed electrode was i n the r o s t r a l b a s o l a t e r a l amygdaloid nucleus ; the most poster i o r was bordering the caudal b a s o l a t e r a l amygdaloid nucleus. Two electrode tip s , one belonging to a D i f f e r e n t Group subject and the other to a Same Group subject were located i n the claustrum. F i n a l l y , two electrode t i p s were situat e d i n the ve n t r a l portion of the caudate, bordering the l a t e r a l amygdaloid nucleus. Table 2 Mean Blood A l c o h o l L e v e l s (q|1) of S u b j e c t s  i n Experiments 1, 2, and 3 Day Experiment Group 1st Treatment Test Same Di f f e r e n t 3.098 2.667 2.957 2.314 E x t i n c t i o n C o n t r o l 3.457 3.314 2.854 3.400 3 Preexposure C o n t r o l 3.248 2.856 3.1 38 2.890 45 Figure 4. Electrode placements of r a t s i n the D i f f e r e n t and Same Groups from Experiment 1. Brain sections were taken from Pellegrino, Pellegrino* and Cushman (1979). 47 Figure 5. Electrode placements of* r a t s i n the E x t i n c t i o n and Control Groups from Experiment 2. Brain sections were taken from Pellegrino. Pellegrino. and Cushman (1979). 48 49 Figure 6. Electrode placements of r a t s i n the CS prexposure and Control Groups from Experiment 3. Brain sections were taken from Pellegrino, Pellegrino, and Cushman (1979). 50 51 General Discussion The purpose of the present t h e s i s mas to determine whether Pavlovian conditioning contributed to the development of tolerance to the anticonvulsive e f f e c t of alcohol. The three studies comprising t h i s t h e s i s attempted to t e s t four p r e d i c t i o n s made from S i e g e l x s Pavlovian theory of drug tolerance ; however. none of these three experiments provided any evidence of the involvement of Pavlovian, conditioning i n the development of tolerance to alcohol's anticonvulsive effect. In Experiment 1. t o l e r a n t subjects tested i n a s a l i n e - p r e d i c t i v e environment were found to be j u s t as t o l e r a n t to the anticonvulsive e f f e c t of alcohol as those tested i n the a l c o h o l - p r e d i c t i v e environment. and s a l i n e administered to t o l e r a n t subjects i n the a l c o h o l - p r e d i c t i v e environment did not e l i c i t a conditioned compensatory increase i n seizure a c t i v i t y . Experiment 2 was an attempt to show that e x t i n c t i o n would accelerate the decline i n tolerance to the anticonvulsive e f f e c t of alcohol. However, because tolerance to the anticonvulsive e f f e c t of alcohol declined completely i n untreated c o n t r o l subjects over the 10-day e x t i n c t i o n phase, i t was not c l e a r whether e x t i n c t i o n procedures are i n f a c t capable of contributing to the decline of t h i s type of a l c o h o l tolerance. However. the rapid decline i n tolerance to the anticonvulsive e f f e c t of alcohol i n nonextinguished subjects suggests that t h i s example of tolerance was not o r i g i n a l l y a product of learning, which has been hypothesized to r e s u l t i n a more enduring change (Siegel. 1975. 1977). In Experiment 3. , the preexposure of the subjects to the environment i n which they subsequently received alcohol did not a f f e c t the ensuing development of tolerance to the anticonvulsive e f f e c t of alcohol. 52 Interpretation of the Results The present r e s u l t s are relevant to two d i f f e r e n t . but ostensibly similar. questions. The f i r s t i s whether or not tolerance to the anticonvulsive e f f e c t of alcohol can develop i n the absence of Pavlovian conditioning. The present experiments provide a c l e a r answer to t h i s question. In each experiment. a s u b s t a n t i a l degree of tolerance was observed i n the absence of the usual i n d i c a t o r s of Pavlovian conditioning. Thus. considered together. the r e s u l t s of the present experiments provide strong evidence that tolerance to the anticonvulsive e f f e c t of alcohol can indeed develop without the contribution of Pavlovian conditioning. The f a i l u r e to f i n d evidence of Pavlovian conditioning i n the present instance i s not subject to the usual c r i t i c i s m d i r e c t e d at negative results, that i s . that the parameters of the experiment were not appropriate f o r the induction of the p a r t i c u l a r e f f e c t under i n v e s t i g a t i o n — i n t h i s case. Pavlovian conditioning. The parameters of the present experiments were c e r t a i n l y appropriate f o r the r e l i a b l e generation of tolerance to the anticonvulsant e f f e c t of alcohol, and i f Pavlovian conditioning were the basis f o r t h i s tolerance, these parameters should have been appropriate f o r the r e l i a b l e generation of conditioning. Clearly, they were not. I t i s possible, a l b e i t unlikely, that Pavlovian conditioning d i d occur i n a l l of the present experiments but was somehow masked. This i s a very r e a l p o s s i b i l i t y i n Experiment 2 i n which the d i s s i p a t i o n of tolerance e f f e c t s was so complete i n c o n t r o l subjects that i t was u n l i k e l y that e x t i n c t i o n procedures would have produced a demonstrable augmentation of t h i s decline even i f they were present. 53 However, the f a c t that tolerance to alcohol's anticonvulsive e f f e c t d i s s i p a t e d so r a p i d l y i n nonextinguished controls does suggest that Pavlovian conditioning was not the mechanism underlying the o r i g i n a l development of the effect. S i e g e l has argued that the conditioned tolerance, l i k e other conditioned effects, i s enduring i n the absence of extinction. For example. he describes a case i n which rat s made tol e r a n t to morphine's analgesic e f f e c t were l e f t i n t h e i r home cages f o r 12 days. and were subsequently found to s t i l l be completely tol e r a n t to morphine's analgesic effect, unlike subjects that had been exposed to e x t i n c t i o n procedures. Can the same c r i t i c i s m also be directed at Experiments 1 and 3? Is i t l i k e l y that the tolerance that developed i n these two experiments was a conditioned response to some feature of the i n j e c t i o n environment that was somehow masked? The problem i n experiments l i k e Experiments 1 and 3 i s that i t i s never c l e a r exactly what feature or features of the i n j e c t i o n environment are serving as the CS. Thus. i t i s never c l e a r that i n j e c t i n g subjects i n another environment has removed the c r i t i c a l CS unless there i s a s u b s t a n t i a l decline i n tolerance as a result. However i n Experiments 1 and 3. the differences between the i n j e c t i o n environment and the a l t e r n a t i v e environment were as great or greater than i n most demonstrations of the s i t u a t i o n a l s p e c i f i c i t y of other alcohol tolerance effects, or f o r that matter the tolerance e f f e c t s of other drugs. The two environments i n Experiments 1 and 3 d i f f e r e d i n terms of experimenter. t e s t i n g chamber c h a r a c t e r i s t i c s , l i g h t , location, and smell. In contrast, environments i n some other studies demonstrating the s i t u a t i o n a l s p e c i f i c i t y of tolerance have d i f f e r e d only i n noise and l o c a t i o n (e. g. . Siegel. 1977) or j u s t l o c a t i o n (e. g. . Melchior & Tabakoff, 1981). This i n d i r e c t evidence 54 suggests that i t i s u n l i k e l y that the f a i l u r e to observe conditioned e f f e c t s u»as due to a masking of extant Pavlovian influences. More d i r e c t evidence against such an argument i s provided by the r e s u l t s of the s a l i n e t e s t i n Experiment 1. On the s a l i n e test, t o l e r a n t subjects were i n j e c t e d with s a l i n e i n the presence of a l l of the cues p r e d i c t i v e of alcohol administration. Accordingly, whatever the c r i t i c a l cue was, i t was present during t h i s test, and according to Siegel's theory the s a l i n e i n j e c t i o n should have e l i c i t e d a compensatory CR. Instead, s a l i n e given i n the presence of the a l c o h o l - p r e d i c t i v e cues produced a small decline i n seizure a c t i v i t y . This provides unequivocal evidence that Pavlovian conditioning does not underlie the development of tolerance to alcohol's anticonvulsant effect. The second but s l i g h t l y d i f f e r e n t question relevant to the present findings i s whether or not Pavlovian conditioning can influence the development of tolerance to alcohol's anticonvulsive effect. Although there i s no evidence of Pavlovian e f f e c t s i n the present experiments, because the same methods were used i n each experiment to produce tolerance, one cannot r u l e out the p o s s i b i l i t y that Pavlovian e f f e c t s might be involved i n tolerance to alcohol's anticonvulsant e f f e c t under other conditions. However, because the conditions of the present experiments (e. g. doses, i n j e c t i o n schedules, routes of administration etc. ) were s i m i l a r to those of studies that have demonstrated environmental c o n t r o l of tolerance and because there was not even a hi n t of Pavlovian conditioning i n the present experiments, i t seems reasonable to assume that Pavlovian conditioning would not influence the development of tolerance to alcohol's anticonvulsive e f f e c t s regardless of the method employed i n t h e i r generation. Thus, 55 i t appears that Pavlovian conditioning can influence some types of alcohol tolerance (e. g. , tolerance to a l c o h o l x s hypothermic and hypnotic e f f e c t s ) but not others (e. g. , tolerance to a l c o h o l x s anticonvulsant e f f e c t ) . Major Implications of the Conclusions One of the two implications of the f a i l u r e to demonstrate conditioned tolerance to the anticonvulsive e f f e c t of alcohol i s that i t l i m i t s the generality of the Pavlovian model of tolerance. Although there have been a number of reports of research on Pavlovian conditioning and tolerance, t h i s trend has been quite recent, and the research that has been done has been confined to only a few e f f e c t s of a l i m i t e d number of drugs (see Table I). To date, most of these studies have obtained support f o r S i e g e l x s theory of tolerance. S i e g e l ( i n press) himself, acknowledges that not a l l instances of tolerance can be conditioned. For example, acute tolerance i s not e a s i l y a t t r i b u t a b l e to Pavlovian conditioning. Acute tolerance r e f e r s to a greater drug e f f e c t on the ascending portion of the blood concentration curve than at the same concentration on the descending portion. In acute tolerance designs, the drug i s adminstered only once, and a l l t r a i n i n g and t e s t i n g are done within that same session. Acute tolerance i s an instance i n which tolerance develops i n the absence of absence of the types of conditioning e f f e c t s described by Siegel. Whether a l l instances of long-term drug tolerance can be conditioned or not i s a question that has not received a great deal of scrutiny. S i e g e l and h i s supporters have claimed that the Pavlovian model applies to many (Cappell, Roach, & Poulos, 1981; Siegel, 1977, i n press; 56 Siegel, Hinson, & Krank, 1979) or a l l (Crowell et al . , 1981; Mansfield & Cunningham. 1980; Siegel. 1977; Siegel. Hinson. & Krank, 1978) cases of drug tolerance. In fact. S i e g e l et al. (1978) make a s p e c i f i c point of s t a t i n g that. "There i s considerable evidence . . . that tolerance does not r e s u l t simply from the organism s u f f e r i n g repeated pharmacological i n s u l t . Instead, tolerance r e s u l t s from repeated a p p l i c a t i o n of the drug i n the context of environmental cues that r e l i a b l y s i g n a l pharmacological stimulation. "(Siegel et al. , 1978, p. 189) The present study c l e a r l y does not support such a claim. There have been only two published reports i n which i t was claimed that an instance of tolerance was not subject to Pavlovian conditioning control. In both, the studies have serious design flaws that cast doubt on the conclusions. In the f i r s t study. Sklar and Amit (1978) attempted to demonstrate that the e x t i n c t i o n procedure described by S i e g e l (1975) would attenuate the l e t h a l e f f e c t s of morphine i n rats. On each of the seven tolerance induction sessions, subjects received increasing doses of morphine such that on Day 1 they received 15 mg/kg of morphine and on Day 7, they received 105 mg/kg morphine. On each of the subsequent 8 days. h a l f the subjects received s a l i n e i n the morphine-associated environment, and the other h a l f remained undisturbed i n t h e i r home cages. On the t e s t day. a l l subjects were i n j e c t e d with 100 mg/kg of morphine—a dose previously determined by Sklar and Amit (1978) to be twice that of the LD50—in the morphine-associated environment. The number of dead animals was used as the dependent measure. No s i g n i f i c a n t differences between the two groups were found ; whereas 6 out of 16 ex t i n c t i o n group r a t s died, 5 out of 16 ra t s i n the con t r o l group died. The authors concluded that they had demonstrated 57 that conditioning e f f e c t s did not a f f e c t tolerance to the l e t h a l e f f e c t s of morphine. A grave problem with t h i s study i s that tolerance to morphine*s l e t h a l e f f e c t s was not demonstrated; i t was only assumed to have developed. I t i s e n t i r e l y possible that no tolerance had developed during the tolerance induction phase. thereby making the experiment e n t i r e l y i rrelevant. In a r e p l i c a t i o n of t h i s study. Siegel. Hinson. and Krank (1979) demonstrated that e x t i n c t i o n procedures could influence tolerance to morphine''s l e t h a l e f f e c t s a f t e r they demonstrated the development of tolerance to the l e t h a l e f f e c t s of morphine. E s p e c i a l l y i n view of t h i s report, the s i g n i f i c a n c e of Sklar and Amit*s experiment i s questionable. In a second study. Demellweek and Goudie (1983) placed amphetamine-injected and s a l i n e - i n j e c t e d r a t s i n an environment. made d i s t i n c t i v e by white noise. dim red i l l u m i n a t i o n and a d i s t i n c t i v e odour, once. 20 min before a 30 min milk-access period and again. 20 min after. Subjects received eight such sessions before the t e s t session during which a l l subjects were i n j e c t e d with amphetamine and tested fo r milk consumption i n the home cages. In order to demonstrate conditioned hyperphagia. these same subjects were given 12 days of ad li b i t u m access to food and water a f t e r the f i r s t t e s t session. before r e c e i v i n g a s a l i n e i n j e c t i o n and access to milk i n the amphetamine-predictive environment. As Demellweek and Goudie (1983) were able to show neither s i t u a t i o n a l s p e c i f i c i t y nor compensatory hyperphagia. they concluded that tolerance to amphetamine %s anorexic e f f e c t was not influenced by environmental manipulations. Unfortunately, a serious methodological problem i n t h i s experiment b e l i e s such a conclusion. Although they exposed subjects to a d i s t i n c t i v e environment during the tolerance development 58 sessions. the amphetamine i n j e c t i o n was always given i n the home cage before the r a t was transferred to the d i s t i n c t i v e environment. Consequently a very s a l i e n t predictor of the e f f e c t s of amphetamine was diss o c i a t e d from the environment i n which the e f f e c t s were experienced. That conditioned hyperphagia was not e l i c i t e d i s not s u r p r i s i n g i n view of the confounding influences of the 12 day i n t e r - t e s t periodi which because i t had some features i n common with the tolerance a q u i s i t i o n phase, may have acted as an e x t i n c t i o n procedure. I t i s c l e a r that t h i s p a r t i c u l a r experiment should be interpretated with caution. There are two published reports i n which some conditioning e f f e c t s were not demonstrable f o r a p a r t i c u l a r instance of tolerance, while other e f f e c t s were. Sherman<1979) showed that whereas he was able to demonstrate e x t i n c t i o n of and a compensatory CR to morphine's hyperthermic effect, he was not able to show s i t u a t i o n a l s p e c i f i c i t y f o r the same e f f e c t of morphine. In addition, he showed that of these three conditioning e f f e c t s only s i t u a t i o n a l s p e c i f i c i t y could be demonstrated f o r morphine's analgesic effect. On the other hand, Eikelboom and Stewart(1981) found that they were able to show s i t u a t i o n a l s p e c i f i c i t y e f f e c t s but not a compensatory CR or e x t i n c t i o n of morphine's hyperthermic effect. Accordingly, these reports d i f f e r from Sklar and Amit's (1978) and Demellweek and Goudie's (1983) i n that some support f o r Siegel's model found. The authors concluded that d i f f e r e n t e f f e c t s of drugs are d i f f e r e n t i a l l y s e n s i t i v e to Pavlovian conditioning influences. In neither report however, did the authors claim that Pavlovian conditioning e f f e c t s do not influence tolerance. Negative r e s u l t s such as those found i n the present experiments create a dilemma f o r researchers. Generally, 59 negative findings are not pursued f o r two reasons (a) they are more e a s i l y a t t r i b u t a b l e to spurious or anomolous factors, and consequently (b) they are not r e a d i l y published. I t i s d i f f i c u l t to determine i f the negative r e s u l t s r e f l e c t a true state of a f f a i r s or are simply, as often i s the case, the r e s u l t of methodological problems. In order to determine the source of the negative findings, further c a r e f u l analysis of the problem i s essential. Investigators are reluctant to do t h i s because of the expenditure of time, e f f o r t and money involved i n such a task. This tendency further complicates the problem of publishing negative r e s u l t s because publishers are r e l u c t a n t to publish reports of negative f i n d i n g s that have not undergone extensive examination. The research on Pavlovian conditioning and tolerance i s a case i n point. There are only a few published studies, reporting the lack of Pavlovian conditioning e f f e c t s i n tolerance. The absence of negative reports has s e r i o u s l y undermined the issue of defining the l i m i t s of the Pavlovian model of tolerance. Without information about the conditions under which Pavlovian conditioning does not a f f e c t drug tolerance, the question of the generality of Siegel*s model cannot be answered. The present studies are the f i r s t c l e a r account of tolerance obtained i n the absence of conditioning effects. By being so, they add i n an important way to the issue of the generality of the model. The second i m p l i c a t i o n of the f a i l u r e to demonstrate that tolerance to the anticonvulsive e f f e c t of alcohol was influenced by Pavlovian conditioning i s that i t does not provide support f o r the Pavlovian i n t e r p r e t a t i o n of contingent tolerance. As previously described, the t y p i c a l paradigm used to demonstrate contingent tolerance i s the before-and-after design, i n which subjects e i t h e r receive the drug before a 60 task or the drug a f t e r the task, during the tolerance development t r i a l s . On the t e s t day, a l l subjects receive the drug before the task. According to Wenger et al . (1981), subjects r e c e i v i n g alcohol before the task f o r the f i r s t time on the t e s t day do not show tolerance because they are not encountering the same cues on t h i s day as they had on the tolerance a c q u i s i t i o n days. For the drug-after-test subjects, the exposure to the t e s t apparatus and performance of the task r e l i a b l y preceded the drug administration on each of the tolerance development sessions. On the t e s t sessions, these subjects do not receive the same cues (test apparatus etc. ) that had previously s i g n a l l e d drug administration. Accordingly, drug-after-test subjects are comparable to the Di f f e r e n t Group subjects of Experiment 1, i n that they a l l receive cues not associated with the drug on the t e s t day. Because the r e s u l t s of the present experiments do not provide support f o r the environmental c o n t r o l of tolerance to alcohol's anticonvulsive effect, a Pavlovian i n t e r p r e t a t i o n of contingent tolerance such as that seen i n the P i n e l et a l . study (1983) i s quite unlikely. Consequently, a theory such as that proposed by Eikelboom and Stewart (1982), which i s a refinment of Siegel's theory, would also not be supported as an explanation of contingent tolerance. To date, there have been no attempts to determine i f contingent tolerance can be explained by any v a r i a t i o n of S i e g e l v s theory. Three studies have reported assessing the Pavlovian i n t e r p r e t a t i o n of contingent tolerance, as suggested by Wenger et al. (1980). Two of the three experiments that have tested the o r i g i n a l hypothesis proposed by Wenger et al. (1980) have serious methodological problems that l i m i t t h e i r conclusions. The t h i r d study, however i s a well c o n t r o l l e d and comprehensive t e s t of the Pavlovian i n t e r p r e t a t i o n of contingent tolerance. 61 The three studies and the contribution of the present experiments to the question of the Pavlovian i n t e r p r e t a t i o n of contingent tolerance are reviewed below. Demellweek and Goudie <1983) showed that tolerance to amphetamine's anorexic e f f e c t was not influenced by environmental manipulations. In addition, they used a before-and-after paradigm to demonstrate contingent tolerance to the same e f f e c t of amphetamine. In order to demonstrate contingent tolerance, r a t s were i n j e c t e d i n t r a p e r i t o n e a l l y with e i t h e r 2 ml/kg of d-amphetamine or volumetric equivalents of saline, 20 min before access to milk. Those subjects that had received amphetamine before milk access were given s a l i n e 20 min afterwards, whereas subjects given s a l i n e before milk access were given d-amphetamine 20 min a f t e r access to milk. There were three amphetamine-before groups, d i f f e r i n g from each other only i n the number of food p e l l e t s given to supplement milk intake; three amphetamine-after groups also d i f f e r i n g i n the amount of food p e l l e t s given were used. Subjects were given 21 drug-milk or milk-drug exposures p r i o r to the t e s t session during which a l l subjects received amphetamine before milk access. A l l three amphetamine-before groups developed s i g n i f i c a n t l e v e l s of tolerance, i n contrast to the three amphetamine-after groups. Demellweek and Goudie(1983) concluded that the opportunity to experience the anorexic e f f e c t s of amphetamine was c r u c i a l to the development of tolerance to amphetamine's anorexic effect. As previously described, the authors claimed that t h e i r attempts to show that Pavlovian conditioning influenced tolerance to amphetamine's anorexic e f f e c t were unsuccessful. However, the previously discussed problems with the experimental design l e f t considerable doubt about t h i s conclusion. Accordingly, t h e i r claims that the r e s u l t s do not support a Pavlovian 62 i n t e r p r e t a t i o n of contingent tolerance are equivocal. Mansfield, Benedict* and Woods(1983) attempted to show environmental c o n t r o l of tolerance to the hypothermic e f f e c t of alcohol and contingent tolerance to the motor d e f i c i t s caused by alcohol. In addition to some methodological problems, the most serious c r i t i c i s m of t h e i r experiment concerns t h e i r conclusions. Conclusions about the Pavlovian i n t e r p r e t a t i o n of contingent tolerance based on observations from two d i f f e r e n t e f f e c t s of alcohol are i n v a l i d . In the t h i r d study, Poulos, Wilkinson, and Cappell (1981) tested the Pavlovian i n t e r p r e t a t i o n of contingent tolerance using amphetamine's anorexic e f f e c t as the behaviour of interest. They i n j e c t e d r a t s i n t r a p e r i t o n e a l l y with 4. 0 mg/kg d-amphetamine 20 min p r i o r to milk access on each of f i v e b i d a i l y tolerance induction days. On the,. t e s t session, conducted 48 hr a f t e r the l a s t tolerance induction session, h a l f of the subjects received an i n j e c t i o n of amphetamine i n the amphetamine-associated environment, whereas the other h a l f received i t i n a novel environment. Rats tested i n the f a m i l i a r environment showed greater tolerance to amphetamine's anorexic e f f e c t than r a t s tested i n the novel environment. Having shown that a s s o c i a t i v e influences affected tolerance, they attempted to determine i f Pavlovian influences could a f f e c t contingent tolerance. Subjects i n two groups received seven b i d a i l y i p amphetamine i n j e c t i o n s and subjects i n two other groups received seven b i d a i l y i p s a l i n e i n j e c t i o n s . One of the groups of subjects r e c e i v i n g amphetamine was allowed a 30-min milk access 20 min a f t e r the i n j e c t i o n whereas the other group was allowed access to the milk on the days i n between injections. A l l of the subjects r e c e i v i n g s a l i n e were allowed access to milk 20 min a f t e r i n j e c t i o n during the tolerance induction phase. On the t e s t day, subjects i n both 63 the amphetamine groups and i n one of the s a l i n e groups mere in j e c t e d with amphetamine 20 min before access to milk. The subjects i n the other s a l i n e group were i n j e c t e d with s a l i n e and allowed milk access, 20 min later. In each group, h a l f the subjects were tested i n the amphetamine-associated environment whereas the other h a l f were tested i n a novel environment. Poulos et al. (1981) argued that i f tolerance to amphetamine xs anorexic e f f e c t were s i m i l a r to that to morphine Ks analgesic effect, then exposure or non-exposure to the tolerance measuring task should not a f f e c t the development of tolerance. The r e s u l t s showed that only the subjects having received amphetamine 20 min p r i o r to milk access developed tolerance. Of these subjects, those tested i n the f a m i l i a r environment showed greater tolerance than those tested i n a completely novel one. They noted that although there was evidence f o r some ass o c i a t i v e influence on contingent tolerance, an unamended Pavlovian hypothesis could not explain why only the contingent group animals developed tolerance. They proposed a r e v i s i o n of the Pavlovian hypothesis i n which the i n s t i g a t i n g stimulus f o r the development of tolerance i s the f u n c t i o n a l consequence of the drug, not j u s t the systemic presence of i t i n the body. Once the homeostatic mechanism, that i s , adaptation to the drug-induced change i s activated, tolerance can be influenced by Pavlovian conditioning effects. Although t h i s r e v i s i o n i s l o o s e l y formulated, i t i s a reasonable one, and i t maybe useful i n studying the r e l a t i o n between contingent tolerance and conditioned tolerance. Certainly, the r e s u l t s of the present experiments do not support the idea of a common mechanism underlying contingent and conditioned tolerance to a l c o h o l K s anticonvulsive effect. P i n e l et al. (1983) demonstrated that r a t s that had undergone 64 amygdaloid seizures during alcohol i n t o x i c a t i o n developed greater tolerance than r a t s that had not undergone amygdaloid seizures while intoxicated. In the present experiments, the development of tolerance to alcohol's anticonvulsive e f f e c t was not shown to be a l t e r e d by Pavlovian conditioning effects. Accordingly, i t i s u n l i k e l y that a Pavlovian conditioning mechanism underlies contingent tolerance to alcohol's anticonvulsive e f f e c t when s p e c i f i c procedures designed to reveal any Pavlovian e f f e c t s did not do so. Indeed, any hypothesis of contingent tolerance i n v o l v i n g a Pavlovian mechanism i s not supported by the present experiments. Concluding Remarks Studies i n v e s t i g a t i n g c l a s s i c a l conditioning e f f e c t s and tolerance, such as the present one are important from both a t h e o r e t i c a l and p r a c t i c a l standpoint. They are c l i n i c a l l y pertinant i n that i t has been suggested by S i e g e l ( i n press) that a Pavlovian mechanism could underlie drug overdose and withdrawal reactions from a drug. Sie g e l argues that the same elements responsible f o r tolerance i n the animal studies are also present i n the c l i n i c a l studies. Accordingly, i n a c l i n i c a l s i t u a t i o n , the drug addict generally associates the drug with c e r t a i n aspects of the drug environment and drug regimen. As i n the animal studies, compensatory CR's develop a f t e r repeated administration i n response to the drug cues (CS's). I f a drug addict receives the drug i n the non-drug-associated environment, the compensatory CR would not be e l i c i t e d and consequently the e f f e c t of the drug would not be counteracted, thereby increasing the p r o b a b i l i t y of the abuser having an overdose. According to S i e g e l (in press), a 65 drug abuser could undergo withdrawal reactions j u s t by mere exposure to the drug environment. There i s some c l i n i c a l support f o r h i s proposal. Sie g e l c i t e s the case of heroin addicts r e c e i v i n g treatment i n a h o s p i t a l situation. Although they are s u c e s s f u l l y treated f o r t h e i r addiction i n the hospital, some soon become readdicted a f t e r leaving the hospital. Noting that often these relapsed addicts return to the environment i n which they were f i r s t addicted to the drug, Sieg e l speculated that the environment e l i c i t e d compensatory CR xs which were subsequently r e l i e v e d by taking the drug. Accordingly, the supposedly "cured" addicts become readdicted. S i e g e l contrasted t h i s s i t u a t i o n with that of the Vietnam vetrans who although addicted to herion i n Vietnam did not s u f f e r the problem of readdiction a f t e r r e h a b i l i t a t i o n as much. He noted that reformed vetrans returned to an environment (United States) completely d i f f e r e n t from that i n which they were i n i t i a l l y addicted. This complete d i f f e r e n c e i n environment gr e a t l y attenuated the chance of e l i c i t i n g the CR's, thereby reducing the chance of readdiction. Some c l i n i c a l observations also suggest that S i e g e l v s model might explain drug overdose. S i e g e l ( i n press) c i t e s the examples of drug addicts, who brought i n to a h o s p i t a l s u f f e r i n g from drug overdose, report that although the dose taken was no greater than usual, t h i s p a r t i c u l a r time, they did not take the drug i n t h e i r usual drug environment. There are very few c l i n i c a l studies i n which c l a s s i c a l conditioning of drug tolerance i s investigated. C l e a r l y though, studies, even those i n v o l v i n g infra-humans, that shed l i g h t on the mechanisms underlying drug tolerance might a i d i n understanding human drug dependence and abuse. Accordingly, the present studies suggest that as i n cases of infra-human tolerance, not a l l instances of human drug dependence can be 66 explained by a Pavlovian mechanism. The present studies have shown that tolerance to the anticonvulsive e f f e c t of* alcohol can develop i n the absence of* c l a s s i c a l conditioning effects. This suggests a l i m i t a t i o n on the generality of the Pavlovian model of tolerance. Without examples of conditions under which a p a r t i c u l a r model does not apply* one obtains a very biased and often inaccurate picture. In fact* no conclusions about the generality of the model can be made. The r e s u l t s of the present study* i n d i c a t e that the Pavlovian model of tolerance does not apply to t h i s very s p e c i f i c case of tolerance studied* that i s * the anticonvulsive e f f e c t of alcohol i n male hooded rats* of a c e r t a i n age and weight* at a c e r t a i n laboratory* etc. X would speculate that i n general* tolerance to the anticonvulsive e f f e c t of alcohol cannot be influenced by c l a s s i c a l conditioning* although no data have been presented i n t h i s t h e s i s to conclusively prove t h i s claim. In any case* the present studies do suggest a l i m i t a t i o n on the generality of the Pavlovian model of tolerance. I t i s clear* however, that an understanding of the s i t u a t i o n s i n which Pavlovian conditioning does and does not influence tolerance would l i k e l y contribute s u b s t a n t i a l l y to our understanding of drug tolerance. 67 Re-Terences Alkana, R. Finn. D. & Malcolm, R. (1928). The importance of experience i n the development of tolerance to ethanol hypothermia. L i f e Sciences, > 32, 2685-2692. Bardo, M. & Hughes, R. (1979). Exposure to a nonfunctional hot plate as a f a c t o r i n the assessment of morphine-induced analgesia and analgesic tolerance i n rats. Fharmacoloqu, Biochemistry, & Behavior, 1&, 481-485. Cappell, H. , Roach. C. , & Poulos, C. (1981). Pavlovian c o n t r o l of cross-tolerance between pentobarbital and ethanol. FsuchQPhflrmacgiqqy' lib 54-57. Carlton, D. & Wolgin, D. (1971). Contingent tolerance to the anor- exigenic e f f e c t s of amphetamine. Phusioloqu and Behavior* 2/ 221-223. — Chen. S. (1968). A study of the alcohol-tolerance e f f e c t and an introduction of a new behavioral technique. Psuchopharmacoloqia, 12. 433-440. Chen. S. (1972). A further note on studies of acquired behavioral tolerance to alcohol. Psychopharmacologia, 27. 265-274. Chen. S. (1979). A c q u i s i t i o n of behavioral tolerance to ethanol as a function of reinforced practice i n rats. Psuchopharmacoloqu, 63. 285-288. Cicero. T. (1980). Alcohol self-adminstration. tolerance and withdrawal i n humans and animals : t h e o r t i c a l and methodological issues. In H. Rigter & J. Crabbe. Jr. (Eds. ). Alcohol tolerance and dependence (pp. 1-51) New York Elsevier/North-Holland Biomedical Press. Commissaris. R. & Rech. R. (1981). Tolerance to pentobarbital and ethanol following chronic pentobarbital administration i n the rat. Substance and Alcohol Actions/Misuse. 2(516). 331-339. Crowell. C. . Hinson. R. . & Siegel. S. (1981). The r o l e of c o n d i t i o n a l drug responses i n tolerance to the hypothermic e f f e c t of ethanol. Psuchopharmacoloqu. 73. 51-54. Dember. W. , Ellen, P. , & K r i s t o f ferson, A. (1953). The e f f e c t s of alcohol on seizure behaviour i n rats. Quarterly  Journal of Studies of Alcohol, 14, 390-394. 68 Demellweek, C. Sc Goudie, A. (1983). An analysis of behavioral mechanisms involved i n the a c q u i s i t i o n of amphetamine anorectic tolerance. Psuchopharmacoloqu, 79, 58-66. Eikelboom, R. & Stewart, J. (1982). Conditioning of drug-induced p h y s i o l o g i c a l responses. Psucholoqical Reyjeuj, J32(5), 507-528. Gibbins, R. , Kalant, H. , & LeBlanc, A. (1968). A technique fo r accurate measurement of moderate degrees of alcohol i n t o x i c a t i o n i n small animals. Journal of Pharmacology and Experimental Theraoutics, 159, 236-242. Greenberg, L. & Lester, D. (1953). The e f f e c t of alcohol on audiogenic seizures of rats. Quarterly Journal of Studies of Alcohol, ±±, 385-389. Hjeresen, D. , Reed, D. , Nakazono, L. , & Woods, S. (1983). Body temperature and ethanol tolerance. Alcoholism : C l i n i c a l and Experimental Research, 7(1), 111. Johnson, R. , Noll, E. , Rodney, W. (1982). S u r v i v a l a f t e r a serum ethanol concentration of 1 1/27.. Lancet, 11(8312), 1394. Kayan, S. , Woods, L. , & Mitchell, C. (1969). Experience as a f a c t o r i n the development of tolerance to the analgesic e f f e c t of morphine. European Journal of Pharmacoloqu, 6j 333-339. Korol, B. , Sletten, I, & Brown, M. (1966). Conditioned p h y s i o l o g i c a l adaptation to a n t i c h o l i n e r g i c drugs. American Journa 1 of Phusioloau, 211(4), 911-914. Krank, M. Hinson, R. , & Siegel, S. (1984). E f f e c t of p a r t i a l r e i n - forcement on tolerance to morphine-induced analgesia and weight l o s s i n the rat. Behavioral Neuroscisnce, 98(1), 72-78. LeBlanc, A. , Gibbins, R. , & Kalant, H. (1975). Generalization of behaviourally augmented tolerance to ethanol, and i t s r e l a t i o n to p h y s i c a l dependence. Psuchopharmacoloqia, 44, 241-256. LeBlanc, A. , Kalant, H. , & Gibbins, R. (1973). Behavioral augmentation of tolerance to ethanol i n the rat. Psuchopharmacoloqia, 30, 117-122. LeBlanc, A. , Kalant, H. , & Gibbins, R. (1976). A c q u i s i t i o n and l o s s of behaviorally augmented tolerance to ethanol i n the rat. Psycho- pharmacology, 48, 153-158. Le, A. , Poulos, C. , & Cappell, H. (1979). Conditioned 69 tolerance to the hypothermic e f f e c t of alcohol. Science/ 306, 1109-1110. Lubou, R. & Moore, A. (1959). Latent i n h i b i t i o n : The e f f e c t of nonreinforced pre-exposure to the conditioned stimulus. Journal of Comparative and Physiological Psychology, 52, 415-419. Mansfield, J. Benedict, R. & Woods, S. (1983). Response s p e c i f i c i t y of behaviorally augmented tolerance to ethanol supports a learning interpretation. Psuchopharmacology, 79, Mansfield, J. & Cunningham, C. (1980). Conditioning and e x t i n c t i o n of tolerance to the hypothermic e f f e c t of ethanol i n ( r a t s ^ J o u r n a l of Comparative and P h u s i o l o a i c a l Psucholoau, Melchiar, C. & Tabakoff, B. (1981). Modification of environmentally cued tolerance to ethanol i n mice. Journal of Pharmacoloau and Experimental Therapuiics, 21?, 175-180. Mucha, R. & Pinel, J. (1977). Postseizure i n h i b i t i o n of kindled seizures. Experimental Neuroloqu,, 54, 266-282. Mucha, R. , Volkovskis, C. , & Kalant, H. (1981). Conditioned increases i n locomotor a c t i v i t y produced with morphine as an unconditioned stimulus, and the r e l a t i o n of conditioning to acute morphine e f f e c t s and tolerance. Journal of Cnmparat.ivp and P h u s i o l o q i c a l Psucholoqu, 95(2), 351-362. Pavlov, I. (1927/1960). Conditioned Reflexes (G. V. Anrep, trans), Oxford U n i v e r s i t y Press, London. Pinel, J. (1980). Alcohol Withdrawal Seizures : Implications of k i n d l i n g Pharmacoloau, Biochemistru, & Behavior, 13 (Suppl. I), 225-231. Pinel, J. , Colborne, B. , Sigalet, P. , & Renfrey, G. (1983). Learned tolerance to the anticonvulsive e f f e c t of alcohol i n rats. Pharmacology, Biochemistru, & Behaviour, _12_<Suppl. 1), 507-510. Pinel, J. & Rovner, L. (1978). Experimental Epileptogenesis : Kindling-induced epilepsy i n rats. Experimenal Neuroloqu, 58, 190-202. Poulos, C. , Wilkinson, D. , & Cappell, H. (1981). 4Homeostatic regulation and Pavlovian conditioning i n tolerance to amphetamine-induced anorexia. Journal of Comparative and p h y s i o l o g i c a l Psucholoqu, J5, 735-746. 70 Randier., A. & Lolordo, V. (1979). Associative and nonassociative theories of the UCS pre-exposure Phenomenon : implications f o r Pavlovian conditioning, sucholoaical Review, 523-548. Roffman, M. , Reddy, C. , & Lali H. (1973). Control of morphine - withdrawal hypothermia by c o n d i t i o n a l stimuli. psuchopharmacoloqia, 59, 197-201. Selle r s , E. & Kalant, H. (1976). Alcohol i n t o x i c a t i o n and withdrawal. Medical Intelligence, 584(14), 757-762. Sherman, J. (1979). The e f f e c t s of conditioning and novelty on the r a t * s analgesic and p y r e t i c responses to morphine. Learning and Motivation, 10, 383-418. Sherman, J. Proctor, C. , & Strub, H. (1982). P r i o r hot plate exposure enhances morphine analgesia i n to l e r a n t and drug-naive rats. Pharmacoloou, Biochemistru, & Behavior, ±JJ 229-232. Siegel, S. (1956). Nonparametric s t a t i s t i c s f o r the behavioral sciences. New York : McGraw-Hill Book Co. Siegel, S. (1975). Conditioning i n s u l i n effects. Journal of Comparative and Phusioloqj.cal Psucholoqu, J32 (3), 189-199. Siegel, S. (1977). Morphine tolerance a c q u i s i t i o n as an as s o c i a t i v e process. Journal •£_ Experimental Psychology : Animal Behavior Processes, J3.(l), 1-13. Siegel, S. (1982). Heroin "overdose" death : contribution of drug-associated environmental cues. Science, 216, 436-437. Siegel, S. ( i n press). C l a s s i c a l conditioning , drug tolerance, and drug dependence. In Y. Is r a e l , F. Glaser, H. Kalant, R. Popham, W. Schmidt, and R. Smart (Eds. ) Research Advances i n Alcohol and Drug Problems. New York : Plenum. Siegel, S. , Hinson, R. , & Kalant, M. (1978). The r o l e of predrug s i g n a l s i n morphine analgesic tolerance : support f o r a Pavlovian conditioning model of tolerance. Jm i r n a i n f Eggerimental Psucholoqu : Animal Behavior Processes, 4J2), Siegel, S. , Hinson, R. , & Krank, M. (1979). Modulation of tolerance to the l e t h a l e f f e c t of morphine by extinction. Behavior Neural Biology, 25, 257-262. Skinner, J. (1971). Neuroscience : A laboratoru manual. Toronto • W. B. Saunders Co. Sklar, L. & Amit, Z. (1978). Tolerance to high doses of 71 morphine : lack of evidence of learning. Behavioral Biology* 22* 509-514. Solomon, R. & Corbit, J. (1973). An opponent-process theory of motivation : I temporal dynamics of affect. Psucholoaical  Review, 81(2), 119-145. Solomon* R. & Corbit, J. (1974). An opponent-process theory of motivation : II. c i g a r e t t e addiction. Journal of Abnormal  Psucholoqu, 81(2), 158-171. Thompson* R. & Ostlund, W. (1965). S u s p e c t i b i l i t y to readdiction as a function of the addiction and withdrawal environments. Journal of Comparative Psucholoqu, _£&( 3), 388-392. Tiffany, S. & Baker, T. (1981). Morphine tolerance i n r a t s : congruence with a Pavlovian paradigm. Journal of Comparative and Ph u s i o l o g i c a l Psucholoqu, 25.(5 7, 747-762. Tiffany* S. , Petrie, E. * Martin, E. , & Baker* T. (1983). Drug sign a l s enhance morphine tolerance development i n hypophysectomized rats. Psychopharmacoloqu, 79, 84-85. Traynor, A. * Shlapfer, W. , & Barondes. S. (1980). Stimulation i s necessary f o r the development of tolerance to a neuronal e f f e c t of ethanol. Journal of Neurobioloqu, 11, 633-637. Wallgren, H. & Barry, H. I l l (1970). Actions of Alcohol. New York : Elsevier, 35-42. Walter, T. & Riccio, D. (1984). Overshadowing e f f e c t s i n the stimulus c o n t r o l of morphine analgesic tolerance. Behavioral  Meuroscience, 97 (4) * 658-662. Wenger, J. , Berlin, B. , & Woods, S. (1980). Learned tolerance to the behaviorally d i s r u p t i v e e f f e c t s of ethanol. Behavior  Neural Biology* 28, 418-430. Wenger, J. * Tiffany* T. , Bombardier* C. , Nicholls. K. , & Woods, S. (1981). Ethanol tolerance i n the r a t i s learned. Science, 213, 575-576. Wikler, A. & Pescor, F. (1967). C l a s s i c a l conditioning of a morphine abstinence phenomenon* reinforcement of opioid-drinking behavior and "relapse" i n morphine-addicted rats. Psuchopharmacoloqia, 10, 255-284. Woolverton, W. & Schuster, C. (1978). Behavioral tolerance to cocaine. National I n s t i t u t e on Drug Abuse Research Monograph. 18. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0096386/manifest

Comment

Related Items