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 using [H-3]naloxone as the ligand. Exposure of ovariectomized rats to estradiol 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 modulates opioid receptor binding in posterior hypothalamic regions involved in gonadotropin secretion and temperature regulation.