Involvement of the mesopallidal dopamine system in ethanol reinforcement.

The current study was designed to test the hypothesis that acquisition of signal-induced anticipation of self-administered ethanol and operant oral self-administration of ethanol increases the extracellular levels of dopamine in the ventral pallidum of alcohol-preferring (P) rats. The study was also designed to explore the association between behavioral activity and dopamine efflux in the ventral pallidum. Adult, female P rats were randomly assigned to operantly self-administer 15% (volume/volume) ethanol, 0.0125% (weight/volume) saccharin, or water. In addition, all groups were acclimated in the operant chambers to periods of habituation, anticipation, and postadministration. The ethanol group showed significant increases in extracellular levels of dopamine in the ventral pallidum during (1). the first 10 min of the anticipation period, (2). the last 10 min of the self-administration period, and (3). the initial 10 min of the postadministration period. There were no significant differences in motor activity during anticipation and self-administration of ethanol, saccharin, or water. These findings support the suggestion that dopaminergic activation in the ventral pallidum is involved in ethanol-seeking and ethanol-drinking behaviors and directly implicate the mesopallidal dopamine system in the reinforcing actions of ethanol.