Biosynthesis of ovarian steroids in the rabbit: influence of progesterone or estradiol implantation into the hypothalamus and limbic structures.

Abstract

The feedback action of progesterone and estradiol implants in the hippocampus amygdala and hypothalamus was investigated and their influence on the incorporation of acetate-1-carbon-14 into ovarian steroids by ovarian homogenate in rabbits was estimated. Progesterone implants in the alverus of the hippocampus markedly increased carbon-14 progestin formation. This region may be part of a positive feedback mechanism that regulates progestin production. Carbon-14-estrogen formation was markedly suppressed by estradiol implants in the medial nucleus of the amygadala which implies that the site is related to the negative feedback control of estrogen formation. Estradiol implants in various sites of the amygdala resulted in a decrease in progestin labeling. Progesterone implants in the medial preoptic area suppressed carbon-14-estrogen formation and those placed in the periventricular arcuate nucleus and the ventromedial hypothalamus nucleus encouraged carbon-14-estrogen formation. It is suggested that the periventricular arcuate nucleus and ventromedial hypothalamus nucleus are involved in different feedback mechanisms for progestin and estrogen formaton and that the medial preoptic area is involved in the reciprocal feedback control of estrogen formation. Estrogen implants inhibited estrogen formation in the medial preoptic area anterior hypothalamic area ventromedial hypothalamic nucleus and periventricular arcuate nucleus and facilitated estrogen formation in the supraoptic nucleus. Estradiol implants in the medial preoptic area anterior hypothalamic area and ventromedial hypothalamic nucleus facilitated progestin periventricular arcuate nucleus.