The limbic system and the control of gonadotropin secretion.

The effects of castration and testosterone propionate (TP) and castration hypophysectomy and castration/hypophysectomy on oxidative metabolism of the amygdala hippocampus and cerebral cortex were studied in adult male rats. Oxygen consumption by the hippocampus and cerebral cortex was not markedly altered in any of the experimental groups. Castration signficantly (p less than .01) increased the oxidative metabolism of the amygdala and the in vitro or in vivo addition of TP did not counter this effect. However the administration of 3.5 mg TP returned the magnitude of oxidative activity of the amygdala to precastration levels. Castration/hypophysectomy and hypophysectomy significantly (p less than .01) decreased the oxygen uptake of the amygdala. Replacement therapy with luteinizing hormone (LH) and follicle stimulating hormone markedly enhanced the oxidative activity of the amygdala both in vivo and in bitro in castrated/hypophysectomized animals. In another study bilateral implants of progesterone in the amygdala and median eminence elevated pituitary stores of LH and decreased hypothalamic stores of LH-releasing factor. The results suggest that the amygdala is sensitive to changing levels of pituitary gonadotropins and may act as a modulator of the "short" feedback effect of anterior pituitary hormones. Also the amygdala may have receptors sensitive to progesterone that are similar to those in the hypothalamus and that they may be involved in hte feedb ack mechanism by which progesterone controls LH secretion.