Involvement of ovarian innervation in steroid secretion

The effects of electrical stimulation of the brain on the ovarian venous plasma concentrations of estradiol (E2) and progesterone (P) were investigated in female rats hypophysectomized and adrenalectomized at 1000 h on the day of proestrus. Stimulation was applied during the proestrous critical period under pentobarbital anesthesia, and contralateral ovarian venous blood was collected from 105-120 min after the stimulation E2 and P concentrations, estimated by RIA, were significantly increased by stimulation of the medial basal prechiasmatic area (PVA), ventromedial hypothalamus, and areas in the mesencephalon and decreased by stimulation of the dorsal hippocampus, lateral amygdala, and mesencephalic areas. Ovarian blood flow was not affected by these stimulations. Ovarian nervotomy in the proestrous rats abolished E2 secretion induced by PVA stimulation. In intact proestrous rats, electrochemical stimulation of the PVA but not the preoptic suprachiasmatic area increased E2 and P concentrations, although stimulation of both areas commonly potentiated gonadotropin secretion. Present findings suggest that the efferent neural system from the brain to the ovaries is supplementary to the brain-pituitary-ovarian hormonal mechanisms in the regulation of ovarian steroid secretion, and the system may be required for the adjustment of ovarian responsiveness and sensitivity to gonadotropins. In addition, evidence for neural feedback on basal FSH secretion in the ovarian-denervated proestrous rats is presented in this study.