Extracellular levels of dopamine in the nucleus accumbens in AA and ANA rats after reverse microdialysis of ethanol into the nucleus accumbens or ventral tegmental area.

摘要

Ethanol is known to increase the release of dopamine in the nucleus accumbens. The question of whether this is a result of a direct or an indirect effect of ethanol on mesolimbic dopaminergic neurons was examined by investigating the extracellular levels of dopamine and its metabolites in the nucleus accumbens of alcohol-preferring AA (Alko Alcohol) and alcohol-avoiding ANA (Alko Non-Alcohol) rats after application of ethanol locally into either the nucleus accumbens or the ventral tegmental area with the use of reverse microdialysis. Application of ethanol (200, 400, or 800 mM in dialysate) into the nucleus accumbens, but not into the ventral tegmental area, temporarily increased the accumbal levels of dopamine in a dose-dependent manner. The ethanol-evoked increase in the level of extracellular dopamine was more prominent in AA rats than in ANA rats. Ethanol tended to suppress levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid. Because the concentrations of ethanol found to elevate the extracellular level of dopamine can hardly be considered pharmacologically relevant, the increase in accumbal dopamine levels after application of ethanol may be due to nonspecific membrane effects of ethanol. The findings support the suggestion that the increase in the extracellular level of dopamine in the nucleus accumbens after systemic administration of ethanol may involve other sites on dopamine neurons or even different neurotransmitter systems, rather than the action of ethanol at the mesolimbic dopaminergic terminals.