Data on the Sites of Stimulatory Feedback Action of Gonadal Steroids Indispensable for Luteinizing Hormone Release in the Rat*

Abstract

The sites of the stimulatory feedback action of gonadal steroids on LH release were investigated in estrogen-primed ovariectomized rats. Either estradiol benzoate (E2) or estrone (E1) injections 72 h after E2 priming induced a significant increase in serum LH 30 h later, whereas injections of progesterone (P) did so 6 h later. Horizontal sections placed above the medial preoptic area prevented the increase after E2 injections but not after E1 and P injections. Retrochiasmatic sections or bilateral lesions placed in the medial-basal part of the suprachiasmatic area prevented any increases in serum LH induced by steroid injections. Intracerebral implantations of E2 and P in E2-primed ovariectomized rats induced a similar significant increase in serum LH when E2 was implanted into the bed nucleus of stria terminalis (BST), the lateral septum (l-SEPT) and the preoptic suprachiasmatic area (POSC), and when P was implanted in to the medial amygdala, the diagonal band of Broca (DBB), the POSC, the l-SEPT and the anterior hypothalamic area (AHA). These results suggest that the stimulatory feedback effect of E2 is exerted on the limbic structures, especially the BST and the l-SEPT, while the main sites of the stimulatory feedback action of P are located in the DBB, the POSC, and the AHA.

Discrete Lesions Reveal Functional Heterogeneity of Suprachiasmatic Structures in Regulation of Gonadotropin Secretion in the Female Rat

“…SCN lesions often attenuated, but never blocked P-induced gonadotro pin release, and ASR and VPC-L lesions did not alter the positive feedback response to P. Thus, the neural system mediating the positive feedback effect of EB appears to be more widely distributed within the suprachiasmatic region than that involved in the positive feedback effect of P. Dif ferential responsiveness to the positive feedback actions of EB and P have also been reported in rats following lesions in other brain areas. For example, knife cuts at the roof of the preoptic area which sever limbic connections to the hy pothalamus, block the positive feedback effect of EB with out interfering with P-induced gonadotropin release [15]. This diffuse vs. circumscribed anatomical organization of EB-and P-sensitive positive feedback systems revealed by lesion studies is closely paralled by a differential distribu tion of estrogen-and progestin-concentrating neurons in the brain.…”

“…Effective lesions have been variously described as involving the su prachiasmatic nuclei (SCN) [1,2,5,7,9,13,27,39], the medial basal suprachiasmatic region [15], the organum vas culosum of the lamina terminalis (OVLT) [26], or the medial preoptic nucleus (MPN), a small periventricular structure lying immediately caudal to the OVLT [36,39,40]. Our re-' This work (publication No.…”

The stimulatory roles of catecholamines and acetylcholine in the regulation of gonadotropin release in ovariectomized estrogen-primed rats.

“…Interestingly, both the BST and 1-SEPT are located within the area indispensable for the stimulatory feedback action of estradiol on LH release in EB-primed ovariectomized rats (Kawakami et al, 1978b). Furthermore, the MPO is a sensitive area to estrone.…”

Effects of diethyldithiocarbamate (ddc), fusaric acid, catecholaminergic and serotonergic receptor blockers on the ascending pathway from the ventrolateral part of the medulla oblongata.

“…3, Fig. 4 (Kawakami et al, 1978). It was reported that the perikarya of the LH-RH neurons are mainly located in the POSC.…”