Sex Differences in Ethanol-induced Dopamine Release in Nucleus Accumbens and in Ethanol Consumption in Rats

In vivo microdialysis was used to examine changes in nucleus accumbens and striatal dopamine, dihydrophenylacetic acid (DO-PAC), and homovanillic acid (HVA) following acute administration of ethanol (0.0, 0.25, 0.5, 1.0, or 2.0 g/kg) in male and female Long-Evans rats. Following dialysis, rats were trained to bar-press for oral ethanol reinforcement. In nucleus accumbens, females showed significant increases in extracellular dopamine following 0.25 or 0.5 g/ kg ethanol, but did not show significant increases over baseline at the higher doses. Males showed slight increases in dopamine at the lower doses and decreased dopamine at 2.0 g/kg. In striatum, both sexes showed increased dopamine at the lower doses and decreased dopamine at 2.0 g/kg. There were slight increases in nucleus accumbens DOPAC and HVA at some doses in both sexes, but no changes in striatal metabolite levels. In addition to showing increased responsiveness to ethanol-induced mesolimbic dopamine stimulation, females consumed more ethanol than males during behavioral testing. The pattern of both greater ethanol-induced nucleus accumbens dopamine release and greater ethanol consumption in females supports the hypothesis that ethanol reward is mediated, at least in part, by the mesolimbic dopamine system.