The effect of estrogen administration in vivo upon catecholamine release in vitro from superfused hypothalamic tissue of ovariectomized pre-pubertal and adult mice

Abstract

In the present report we examined the effects of estrogen upon catecholamine release from superfused medial basal hypothalamic tissue fragments of pre-pubertal ovariectomized CD-1 mice. Prepubertal mice treated with estradiol benzoate (EB--5 micrograms x 2 days, sc), showed significantly reduced amounts of dopamine but no changes in norepinephrine release in response to a depolarizing concentration of potassium (30 mmol/L) compared with their respective groups receiving the oil vehicle. Since EB treatment reduced potassium stimulated dopamine release in these pre-pubertal mice, in a second experiment we compared the effects of EB versus oil vehicle treatment upon potassium stimulated dopamine release from the hypothalamus of the ovariectomized adult female mouse. Similar to that observed in the pre-pubertal mouse, EB treatment significantly reduced the amount of potassium stimulated dopamine release. Interestingly, the absolute amounts of potassium stimulated dopamine release was substantially greater in adult compared with pre-pubertal mice. These results demonstrate that the hypothalamic dopaminergic system of both pre-pubertal and adult mice show relatively similar responses to estrogen treatment but differ in absolute amounts of dopamine released.