Lack of tolerance to ethanol-induced dopamine release in the rat ventral striatum

The effect of ethanol challenge on the extracellular concentrations of dopamine, 3,4-dihydroxy-phenylacetic acid and homovanillic acid was studied in the ventral striatum of rats repeatedly treated with ethanol. Ethanol-treated animals (1 g/kg i.p. twice a day for 12 days) developed marked tolerance to the behavioral signs of ethanol intoxication when challenged with ethanol (2 g/kg i.p.). However, in ethanol-treated animals the increased output of dopamine and metabolites after ethanol challenge (1 or 2 g/kg i.p.) was not statistically different from that observed in saline-treated rats. These results indicate that tolerance does not develop to the ethanol-induced stimulation of dopamine release and support the hypothesis that activation of the mesolimbic dopamine system contributes to the reinforcing properties of ethanol.