Distribution of Gonadotropin-Releasing Hormone in the Rat Brain as Observed with Immunocytochemistry¹

Abstract

The distribution of gonadotropin-releasing hormone (GnRH) was studied in the brain of adult female rats with three immunocytochemical techniques using antisera to unconjugated synthetic GnRH and to GnRH conjugated with limpet hemocyanin. GnRH was found in nervous tissue surrounding blood vessels of the organum vasculosum of the lamina terminalis. In the median eminence it occurred in nervous tissue associated primarily with the tuberoinfundibular sulci throughout their extent. Cephalic to the pars tuberalis GnRH often spread across the median eminence from sulcus to sulcus. Caudally, with widening of the median eminence, GnRH occurred dorsal to the tuberoinfundibular sulci, and especially in the external lamina medial to the sulci. A broad median zone of the median eminence was rather free of GnRH. GnRH was most concentrated in the region of continuity between the dorsolateral walls of the infundibulum and floor of the third ventricle where the tuberoinfundibular sulci are deep. Caudal to the infundibulum GnRH was disposed in a flat zone through the cephalic portion of the floor of the mammillary recess. In the median eminence GnRH appeared to be located in axons that terminated there. The amount of demonstrable GnRH varied significantly from rat to rat. The distributions of GnRH as revealed by use of antisera to unconjugated and conjugated GnRH were essentially the same. The apparent order of sensitivity of the immunocytochemical methods was: the peroxidase-antiperoxidase (PAP) (Sternberger et al.) procedure greater than the immunoglobulin-enzyme bridge (Mason et al.) procedure smaller than the conjugated antibody (Nakane and Pierce) procedure.

Efferent Projection of the Nucleus <i>Praeopticus Medians</i>to the Median Eminence in Rats

“…W heaton et al [1975] presented LH-RH localization in the rat hypothalamus using radio immunoassay; LH-RH is concentrated in the medial basal preoptic tissue and distributed in the arcuate-median eminence region extending to the lateral aspect of the ventromedial nucleus. A concentration of LH-RH fibers in the median eminence was demonstrated by Sétâlô et al [1975] and Baker et al [1975]. In this context, the degenerated nerve terminals revealed in the present study may contain LH-RH.…”

Immunocytology of Luteinizing Hormone-Releasing Hormone

“…The median eminence (ME) provides the region of most intense immunocytological visualization of luteinizing hormone-releasing hormone (LH-RH) fibers in a variety of vertebrates, including frog [Alpert et al, 1976;Goos et al, 1976], toad [Doerr-Schott and D ubois, 1975], duck [Calas et al, 1974;McNeill et al, 1976], cockerel [de Reviers and D ubois, 1974], guinea pig [Leonardelli et al, 1973;Barry and D ubois, 1974a; Baker et al, 1974;Silverman, 1976], rat [Baker et al, 1974[Baker et al, , 1975; King et al, 1974;Kordon et al, 1974;Pelletier et al, 1974;G oldsmith and G anong, 1975;Setalo et al, 1975Setalo et al, , 1976Hoffman, 1976], mouse [Zimmerman et al, 1974;Baker et al, 1974;Leonardelli et al, 1973;G ross, 1976;Hoffman, 1976], hamster [Pickard and Silverman, 1976], cat [Barry and D ubois, 1974a[Barry and D ubois, , 1975[Barry and D ubois, , 1976Bugnon et al, 1976b], dog [Bugnon et al, 1976b;Dubois, 1974a, 1975], squirrel monkey [Barry and Carette, 1975], rhesus monkey , and human fetus [Bugnon et al, 1976a]. Electron microscopic examination of the ME identi fied LH-RH within granules [Pelletier et al, 1974;G oldsmith and G anong, 1975;Silverman and D esnoyers, 1975], These could be categorized into 2 groups: granules 90 to 120 nanometers in diameter found mainly in axons, and granules 40 to 70 nanometers in diameter found in nerve terminals [Silverman and D esnoyers, 1975].…”

Failure of neurotransmitter blockers to alter PGE2-induced LH release.

“…mediated via the adenylate cyclase-cyclic-AMP system, the results reported here suggests that PGE2 does not act transsynaptically, but rather acts post-synaptically directly on LH-RH neurons or other LH-RHsecreting elements (Wheaton et al, 1975Baker et al, 1975.…”