Alcohol-preferring rats: genetic sensitivity to alcohol-induced stimulation of dopamine metabolism.

The effect of ethanol on brain dopamine (DA) metabolism in the caudate nucleus (CN), olfactory tubercle (OT) and medial prefrontal cortex (MPFC) was compared in two selectively bred rat lines, one ethanol preferring and the other ethanol nonpreferring. Male rats from the 16th and 17th generations of both lines that never experienced ethanol beforehand were used. No differences in the basal concentrations of DA and its metabolites, DOPAC and HVA, in the above brain regions were found between the two lines. The oral administration of 2 g/kg of ethanol to ethanolnonpreferring rats increased DOPAC and HVA and reduced DA levels in the CN and OT but was ineffective in the MPFC. On the other hand, ethanol administration to ethanol-preferring rats decreased DA content and increased DOPAC and HVA levels, not only in the CN and OT, but also in the MPFC. Moreover, the changes induced by ethanol on DA metabolism in the latter group were significantly greater than in ethanol nonpreferring rats. These results indicate that ethanol preferring rats have a genetic high sensitivity to the ethanol effect on DA metabolism, and suggest that such a trait might play a role in ethanol preference.