Sex Differences and Effects of Estrogen on Dopamine and DOPAC Release from the Striatum of Male and Female CD-1 Mice

In the present study, we directly compare striatal dopamine metabolism in gonadectomized male and female CD-1 mice treated with 2 days of estrogen or oil vehicle. Basal and potassium-stimulated dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) release from in vitro superfused striatum as well as pre- and postsuperfusion tissue dopamine contents were measured. Both basal and potassium-stimulated dopamine release were significantly higher and DOPAC release was significantly lower in males than in females. However, striatal tissue dopamine content was lower in males than in females. Estrogen-treated female mice showed increased basal and potassium-stimulated dopamine release compared to oil-treated females without affecting tissue dopamine content. Estrogen did not affect striatal dopamine concentrations or release in males. These results demonstrate clear sex differences in striatal dopamine turnover and concentrations under conditions of equal hormonal status. The results also indicate that estrogen can exert substantial effects on striatal dopamine metabolism by acting specifically in females to increase neuronal dopamine synthesis and release without depleting dopamine content. These results have important implications for the observed sex differences in clinical movement disorders such as Parkinson's disease.