Ethanol exposure differentially alters central monoamine neurotransmissionin alcohol-preferring versus -nonpreferring rats

Individual differences in ethanol preference may be linked to differences i n the functional activity of forebrain monoamine systems or their sensitivi ty to modification by ethanol. To test this hypothesis, basal extracellular concentrations of dopamine (DA) and serotonin (5-HT) in the nucleus accumb ens as well as the effects of repeated ethanol pretreatment on the basal re lease of these transmitters were examined in alcohol-preferring (P), alcoho l-nonpreferring (NP), and genetically heterogeneous Wistar rats. Ail animal s received i,p. injections of ethanol (1.0 g/kg) or saline for 5 consecutiv e days. Fifteen hours after the final pretreatment, basal extracellular con centrations and "in vivo extraction fraction" Values for DA and 5-HT were d etermined by no-net-flux in vivo microdialysis. in ethanol-naive rats, sign ificant line differences were observed with high basal 5-HT release in P ra ts, low 5-HT release in NP rats, and intermediate 5-HT levels in Wistar rat s. No differences among groups were noted in basal DA release. Ethanol pret reatment decreased basal extracellular 5-HT levels in P rats whereas increa sing 5-HT efflux was seen in the Wistar and NP lines, in addition, ethanol pretreatment increased extracellular DA concentrations in Wistar and P rats , but not in NP rats. The results confirm a relationship between the functi onal status of forebrain DA and 5-HT systems and ethanol preference or aver sion. Moreover, the data suggest that ethanol exposure can alter basal DA a nd 5-HT in the nucleus accumbens and that vulnerability to ethanol-induced changes in monoamine neurotransmission may be a factor in genetically deter mined ethanol preference.