Effect of estradiol treatment on β-endorphin content and release in the female rat hypothalamus

Abstract

The purpose of the present study was to determine whether an injection of estradiol valerate or chronic estradiol treatment alters beta-endorphin-immunoreactive (IR) material in the hypothalamus. Hypothalamic beta-endorphin-IR material was significantly reduced (by 47%) 2 months following an estradiol valerate injection. In addition, both the basal and veratridine-evoked release of beta-endorphin-IR material from hypothalamic slices incubated in vitro were decreased 48% and 52%, respectively. The net release of beta-endorphin-IR material was decreased by 50% compared to control animals. Chronic estradiol treatment (2 months) did not alter the tissue content of beta-endorphin-IR material. Although, we noted a significant decrease (48%) of the basal release and a significant increase (45%) of the evoked release, the net release of beta-endorphin-IR material from slices was not altered (107% of control). The present results suggest that estradiol valerate treatment decreases the capacity of beta-endorphin neurons in the hypothalamus to synthesize and maintain the release of beta-endorphin.