Gonadotropin-releasing hormone (GnRH) neurons and pathways in the rat brain

Abstract

Gonadotropin-releasing hormone (GnRH) neurons and their pathways in the rat brain were localized by immunocytochemistry in 6- to 18-day-old female animals, by use of thick frozen or vibratome sections, and silver-gold intensification of the diaminobenzidine reaction product. GnRH-immunoreactive perikarya were observed in the following regions: olfactory bulb and tubercle, vertical and horizontal limbs of the diagonal band of Broca, medial septum, medial preoptic and suprachiasmatic areas, anterior and lateral hypothalamus, and different regions of the hippocampus (indusium griseum, Ammon's horn). In addition to the known GnRH-pathways (preoptico-terminal, preoptico-infundibular, periventricular), we also observed GnRH-immunopositive processes in several major tracts and areas of the brain, including the medial and cortical amygdaloid complex, stria terminalis, stria medullaris thalami, fasciculus retroflexus, medial forebrain bundle, indusium griseum, stria longitudinalis medialis and lateralis, hippocampus, periaqueductal gray of the mesencephalon, and extracerebral regions, such as the lamina cribrosa, nervus terminalis and its associated ganglia. By use of the silver-gold intensification method we present Golgi-like images of GnRH perikarya and their pathways. The possible distribution of efferents from each GnRH cell group is discussed.

A neuroanatomical and neuroendocrinological study into the relationship between social status and the GnRH system in cooperatively breeding female Damaraland mole-rats, Cryptomys damarensis

“…In contrast, those found in the sheep (Lehman et al 1986), springbok (Robinson et al 1997) and rhesus monkey have been reported to have a more complex morphology. It should be noted that the number of bipolar neurones identified in the present study may have been underestimated; many of the apparently unipolar GnRH cells in the rat brain have been shown to be bipolar using silver -gold intensification of the immunocytochemical staining (Merchenthaler et al 1984). In the male Djungarian hamster, differential changes in the incidence of these morphological subtypes have been observed during sexual maturation (Yellon & Newman 1991).…”

“…The GnRH neurones in the Damaraland mole-rat are predominantly unipolar and bipolar, as found in many mammals including the rat (Witkin et al 1982, Merchenthaler et al 1984, white-footed mouse (Glass 1986), Syrian hamster (Jennes & Stumpf 1980) and mink (Ntoumi et al 1992). In contrast, those found in the sheep (Lehman et al 1986), springbok (Robinson et al 1997) and rhesus monkey have been reported to have a more complex morphology.…”

“…This variability may be associated with their unusual migration from the olfactory placode (Schwanzel-Fukuda & Pfaff 1989). In the opossum, Monodelphis domestica, GnRH cell bodies do not migrate into the preoptic area (SchwanzelFukuda et al 1988), but in the rat, they do not reach into the MBH (Witkin et al 1982, Merchenthaler et al 1984. In contrast, in the mink approximately 7% of GnRH cell bodies are located in the POA and 80% in the MBH (Ntoumi et al 1994).…”

Neuroendocrine Regulation of GnRH Release in Induced Ovulators

“…It is possible that GnRH neurons actually form an interconnected network. Synapses have been shown between GnRH neurons (40,41,128,146,213,240). In addition, in vitro studies (119) of GT1-7 cells, the immortalized mouse GnRH neuronal cell line, showed that these cells expressed the message and the protein for the GnRH-receptor.…”

Expression of gonadotropin-releasing hormone receptors and autocrine regulation of neuropeptide release in immortalized hypothalamic neurons.

“…The major regulator of reproduction in mammals, gonadotropin-releasing hormone (GnRH), is produced by neuronal cells located in the preoptic area and adjacent sites in the rostral portion of the hypothalamus and secreted into the hypophyseal portal vessels at the median eminence (1,2). The secretion of GnRH occurs in an episodic manner due to the activity of a hypothalamic GnRH pulse generator (3).…”