Effects of estradiol on the basal and evoked efflux of norepinephrine and 5-hydroxytryptamine from slices of rat hypothalamus.

17-beta-Estradiol, at a concentration (100 ng/ml) approaching plasma levels found in pregnant women, inhibited the K+-evoked efflux of endogenous norepinephrine from superfused slices of rat hypothalamus. The same concentration of estradiol increased slightly the basal efflux of serotonin. Since estradiol crosses the blood-brain barrier with ease it is suggested that the inhibition of norepinephrine release from central neurons may contribute to the depression and emotional lability sometimes associated with estradiol therapy.