ENVIRONMENTAL ENRICHMENT ATTENUATES LOCOMOTOR SENSITIZATION, BUT NOT IN-VITRO DOPAMINE RELEASE, INDUCED BY AMPHETAMINE

Rats were raised from weanling until young adulthood in either an enri ched condition (EC) or isolated condition (IC). Following this, the lo comotor and rewarding effects of amphetamine were determined using the conditioned place preference (CPP) paradigm. EC rats were more sensit ive to the acute locomotor stimulant effect and rewarding effect of am phetamine relative to IC rats. In contrast, EC rats were less sensitiv e than IC rats to the locomotor sensitization effect obtained across r epeated amphetamine injections. To determine the effect of environment al enrichment on alteration of brain dopamine (DA) function induced by amphetamine, the effect of amphetamine on electrically evoked release of DA and dihydroxyphenylacetic acid (DOPAC) was determined in vitro using tissue slices from the nucleus accumbens and striatum of EC and IC rats. No differences between EC and IC rats in release of DA or DOP AC were evident, suggesting that the environmentally induced differenc e in sensitivity to the behavioral effects of amphetamine involves a n eural mechanism extrinsic to the mesolimbic and nigrostriatal terminal field legions.