Increase in dopamine content of the rat median eminence after long-term ovariectomy and its reversal by estrogen replacement.

The norepinephrine (NE) and dopamine (DA) concentrations of the median eminence and the remaining hypothalamus of female rats were assayed using a sensitive radioenzymatic method. There were no changes in the catecholamine concentrations of either brain region when measured in the mornings of the different days of the estrous cycle. Four to 5 weeks after ovariectomy there was a marked increase in the DA but not the NE content of the median eminence, and the daily administration of estradiol benzoate for 7 days prior to sacrifice reversed the ovariectomy-induced increase in DA. Ovariectomy did not alter catecholamine concentrations in the remaining hypothalamus.