Effects of suprachiasmatic nucleus lesions on hypothalamic LH-releasing hormone (LHRH) content and gonadotropin secretion in the ovariectomized (OVX) female rat.

Suprachiasmatic nucleus lesions in OVX rats blocked progesterone-induced gonadotropin surges without affecting tonic levels of these hormones or the expression of estrogen negative feedback. In addition, these lesions resulted in a decrease in LHRH content of tissue rostral and caudal to the lesion. These results suggest that the effect of suprachiasmatic nucleus lesions on phasic gonadotropin secretion may be due to the interruption of LHRH input to the median eminence from rostral centers known to be important in this event.