Involvement of Ovarian Innervation in Steroid Secretion*

Abstract

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-pituitaryovarian 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. {Endocrinology 109: 136, 1981) I T HAS been demonstrated in rats that the cyclic alteration of ovarian steroid biosynthesis (1) and secretion (2, 3) are temporally related to the cyclic changes of gonadotropin secretion throughout the estrous cycle. The administration of gonadotropins to cyclic rats increased or decreased ovarian biosynthetic activity (1), and the effects were altered qualitatively and quantitatively during the estrous cycle (1, 4). However, it is still obscure whether the cyclic changes in ovarian steroid synthesis and release depend only upon gonadotropin secretion. Stimulation of the dorsal hippocampus (d-HPC) during the estrous cycle changed steroid biosynthetic activity without affecting gonadotropin secretion (4) or pituitary stalk blood LHRH concentration (5). More recently, d-HPC stimulation was shown to induce alterations in ovarian estrogen and progestin biosyntheses in pituitary-lesioned rabbits pretreated with 20a-hydroxyprogesterone (6). The above findings indicate the existence of other mechanisms besides the gonadotropin regulation of ovarian steroid synthesis and release.Recently, adrenergic and cholinergic projections to the

Adrenergic intracerebroventricular stimulation affects progesterone concentration in the ovarian vein of the rat: participation of the superior ovarian nerve

“…Thus, electrical stimulation of some central nuclei affect progesterone and oestradiol release from the ovary (Kawakami et al 1981) without any changes in gonadotrophins (Kawakami et al 1972) or gonadotrophinreleasing hormone (GnRH) release (Chiappas et al 1977).…”

Hormones and the hippocampus

“…Notably, in some instances at least, the mechanism of control may bypass the HPA axis and take place through direct innervation of body organs probably including the ovary, liver, kidney, bone marrow, spleen and thymus (Kawakami et al 1981, Seto et al 1988, Ader et al 1991) and the adrenal (Parker et al 1993).…”

Vasoactive intestinal peptide induces the synthesis of the cholesterol side-chain cleavage enzyme complex in cultured rat ovarian granulosa cells.

“…While the hormonal regulation has been extensively investigated, much less attention has been given to the neural regulatory component (4,5). Recently, the presence of ovarian peptidergic nerves (6,7) has been thoroughly documented (8,9).…”