Effects of castration, steroid replacement, and sexual experience on mesolimbic dopamine and sexual behaviors in the male rat.

The concentrations of dopamine (DA) and a DA metabolite in a terminal field of the mesolimbic DA system, the nucleus accumbens, decreased after castration, an effect that was prevented by treatment with testosterone (T) or estradiol. After castration, DA concentrations were increased in the medial preoptic area, and were unchanged in the caudate-putamen, substantia nigra, and ventral tegmental area. Changes in DA and DA metabolite concentrations in the nucleus accumbens coincided with changes in measures of sexual arousal. Sexual experience did not affect DA concentrations, but did increase DA metabolism in the nucleus accumbens, and also increased the frequency of female-directed behavior in castrated males. These results suggest that T, or its aromatized metabolite, influences the mesolimbic DA system, and that this system is involved in mediating sexual arousability.