ESTROGEN REGULATION OF MU-OPIOID RECEPTOR DENSITY IN HYPOTHALAMIC PREMAMMILLARY NUCLEI

The effect of estradiol on opioid receptor density in the hypothalamus of female rats was examined by in vitro receptor autoradiography usin g [H-3]naloxone as the ligand. Exposure of ovariectomized rats to estr adiol for 48 h markedly increased the density of [H-3]naloxone binding in both the ventral and dorsal premammillary nuclei but not in other regions of the hypothalamus or amygdala. Thus, estrogen selectively mo dulates opioid receptor binding in posterior hypothalamic regions invo lved in gonadotropin secretion and temperature regulation.