ISOLATION REARING IN RATS - PRESYNAPTIC AND POSTSYNAPTIC CHANGES IN STRIATAL DOPAMINERGIC SYSTEMS

Isolation rearing of rats produces a behavioral syndrome indicative of altered dopamine (DA) function in the nucleus accumbens (NAC). The pr esent experiments extend these findings by investigating: (a) interact ions between isolation rearing and repeated handling/testing on presyn aptic DA function in the NAC using in vivo microdialysis; (b) the dose -response curve for the effects of d-amphetamine, and the responses el icited by high potassium, using in vivo microdialysis; and (c) postsyn aptic function in isolates as indexed by DA receptor-linked cAMP produ ction. Experiment 1 showed that both isolation rearing and repeated ha ndling/testing had effects on monoamine function in the NAG. However. while both manipulations enhanced DA release evoked by d-amphetamine, only isolated rats had elevated basal DA levels. Opposite neurochemica l changes were observed with respect to the serotonin metabolite 5-HIA A, isolates having lower, and repeatedly handled/tested animals having higher, extracellular levels. Experiment 2 provided evidence for enha nced d-amphetamine-evoked DA release in isolated animals, while potass ium-evoked DA release was reduced. Experiment 3 provided evidence that the isolation rearing induced changes in presynaptic DA function were accompanied by postsynaptic changes. Specifically, the inhibitory inf luence of the D-2 receptor on D-1 receptor-stimulated cAMP production was attenuated in ventral striatal slices taken from isolates, suggest ing a functional downregulation of D-2 receptors. (C) 1998 Elsevier Sc ience Inc.