Site of positive feed back of ovarian hormones in immature female rats

A single in jection of 50 I. U. PMS on day 28 produced ovulation on day 31. Systemic anesthetization by Nembutal on days 28 and 29 did not delay PMS induced ovulation, however, administration of Nembutal at 30 days of age, the day prior to PMS induced ovulation, did delay ovulation. Direct anesthetization by Nembutal of the preoptic area and the lateral septum on day 29 delayed the induction of precocious ovulation by PMS whereas injection into the mammillary body, basal part of the amygdala complex, or frontal cortex had no apparent effect. Also, a direct injection of Nembutal into the preoptic area before or during the critical period (2 to 4: 00 P. M.) was successful in delaying ovulation. However, if injection was made after the critical period the animal ovulated on schedule. No ovulation after PMS administration in hypophysectomized rats was found, however, a significant uterine weight increase was observed. In rats with prior intrasplenic ovarian grafts no significant histological differences were observed between ovaries of rats treated with PMS and those not treated. In rats given PMS and injected with metopirone twice daily for three days, ovulation was delayed. In those animals adrenalectomized and pre-treated with PMS, and given metopirone, ovulation was also delayed. However, adrenalectomized rats not injected with metopirone ovulated at the normal day for PMS induced ovulation. Although anesthetizing with Nembutal systemically on the day prior to PMS induced ovulation blocked this ovulation, an injection of metopirone did not.