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Effects of in-vivo stimulation of the rat ventral subiculum on the expression of presynaptic proteins in the nucleus accumbens, the prefrontal cortex, and the dorsal striatum Lam, Clayton

Abstract

The present project focuses on changes on the expression of presynaptic proteins at synaptic junctions in the core of the nucleus accumbens (NAc), the shell of the NAc, the prefrontal cortex (PFC), and the dorsal striatum (STR) after repeated electrical stimulation of the subicular projection from the ventral hippocampus of rats. Related research in Dr. Phillips' laboratory has shown that comparable stimulation caused an increased release of dopamine in the N A c and hyperlocomotion. The purpose of this thesis is to investigate possible changes in presynaptic protein concentration in response to repeated stimulation of the ventral subiculum (vSub) at parameters shown previously to potentiate locomotor activity and DA efflux in the NAc. The first series of experiments confirmed that repeated vSub stimulation caused an increase and potentiation of locomotor activity. The second series of experiments investigated the effect of repeated vSub stimulation on the expression of presynaptic proteins in the four brain regions. Five presynaptic proteins were quantified by enzyme-linked immunoabsorbent assay (ELISA) technique and they were synaptophysin, syntaxin, SNAP-25, complexin I and complexin II. The analysis of variance (ANOVA) was used to analyze group and regional differences in the expression of each presynaptic protein. All presynaptic proteins showed a significant difference between the stimulation group and the control group. Regional differences in the expression of most presynaptic proteins including synaptophysin, complexin I, complexin II and complexin II/I ratio were highly significant except for syntaxin. The group x region interaction of complexin II/I ratios was significant. This interaction indicated that regional differences in the relative expression of the two complexin proteins may be caused by vSub stimulation. The last analysis examined the correlation between the expression of presynaptic proteins and locomotor activity. The immunoreactivity of syntaxin in the core of the NAc showed a significantly high correlation with locomotor activity. This finding suggests that presynaptic proteins may be part of the subcellular mechanism in regulating vSub-induced locomotor activity.

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