Effects of estrogen upon dopamine release from the corpus striatum of young and aged female rats.

In vitro superfusion was used to examine the effects of estrogen administration upon striatal dopamine release in ovariectomized young and aged female Fischer 344 rats in response to 10 microM amphetamine or 30 mM potassium stimulation. Estrogen treatment increased basal dopamine and decreased DOPAC release in young and aged females (10 micrograms estradiol benzoate given subcutaneously 24 and 48 h prior to superfusion). Amphetamine-stimulated dopamine release was significantly decreased in aged estrogen-treated females, but did not differ in young females as a function of estrogen treatment. Conversely, young females treated with estrogen showed significantly decreased striatal dopamine release in response to potassium stimulation, while aged females showed no differences as a function of hormone treatment. Striatal dopamine content was significantly decreased in all estrogen-treated young and aged females. It appears that estrogen is altering dopamine uptake mechanisms in both age groups, since basal DOPAC release is decreased and dopamine is increased. This estrogen effect depletes the readily releasable dopamine storage pool to a greater extent in the aged female as evidenced by reduced amphetamine-stimulated dopamine release. By contrast, estrogen does not alter vesicular dopamine storage pools in aged females, which are mobilized by potassium. These results may have important implications regarding sex differences in expression and treatment of age-related movement disorders.