The location of LH-RH neurons in the rat hypothalamus and their pathways to the median eminence

Abstract

The location of the perikarya of LH-RH neurons in the rat hypothalamus and their pathways to the median eminence were studied by immunohistochemistry and radioimmunoassay after placing stereotaxic electrolytic lesions in several parts of the hypothalamus. The principal location of the cell somata was found to be in the ventral part of the medial preoptic area; their pathways were classified into a main baso-lateral pathway and an accessory descending pathway branching off from the former. The main pathway was found to cross in the vicinity of the corresponding neuronal perikarya. The central median eminence and the dorsal and ventral walls of the tubero-infundibular sulcus of the caudal part of the median eminence are innervated mainly by the baso-lateral pathway. On the other hand, the rostral and most caudal protions of the median eminence are innervated principally by the descending pathway and have a subsidiary dual innervation. The projection of LH-RH neurons to the OVLT is believed to originate from perikarya adjacent to this circumventricular organ.

Immunocytological study of the chronology of pituitary cytogenesis in the domestic pig (Sus scrofa) with special reference to the functioning of the hypothalamo-pituitary-gonadal axis

“…This topography, very similar to that reported in guinea-pigs Setalo et al, 1976a ;Jennes and Stumpf, 1980), cats (Barry andDubois, 1974a, 1975) and rats (Naik, 1975a, b ;Setalo et al, 1976b ;Ibata et al, 1979), was obtained in young fetuses (60 and 70 days) and may therefore be different from adult distribution.…”

Morphological Interactions between Glial Fibrillary Acidic Protein (GFAP)-like Immunoreactive Elements and Lutenizing Hormone Releasing Hormone (LHRH)-like Immunoreactive Nerve Endings in the Median Eminence of the Rat. Double Labeling Immunoelectron Microscopic Study.

“…These nerve processes projected to the lateral part of the external layer of the ME through the main baso-lateral pathway and the accessory descending pathway [11,13]. In the present study, these LHRH-LI nerve endings were observed to make intimate contact with GFAP-LI astrocytes in the subependymal cell layer and processes of tanycytes with GFAP-like immunoreactivity in the palisade layer of the ME.…”

“…From their location, therefore, one possibility that they may be involved in the regulation of release of the R/I H to the portal vessels is considered. Lutenizing hormone releasing hormone (LHRH) is a typical R/I H, and their nerve endings have been demonstrated in the pericapillary region of the ME and they show a specific regional distribution in the ME [11][12][13]16]. Therefore, it is of interest to elucidate their fine structural interactions.…”

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

“…It was reported that the perikarya of the LH-RH neurons are mainly located in the POSC. (Setalo et al, 1976, Ibata et al, 1979. From the present findings, it may be deduced that the noradrenergic pathway originating in the A1 supplies noradrenaline to the preoptic-anterior hypothalamic area, including the POSC, via the ventromedial tegmental area and the lateral hypothalamic area for the induction of proestrous gonadotropin surges.…”