The distribution of growth‐hormone‐releasing factor (GRF) immunoreactivity in the central nervous system of the rat: An immunohistochemical study using antisera directed against rat hypothalamic GRF

Abstract

Immunohistochemical methods have been used to chart the distribution of rat hypothalamic growth-hormone-releasing factor (rhGRF) immunoreactivity in the brains of normal and colchicine-treated adult albino rats. The results suggest the existence of at least two distinct rhGRF-containing systems: one responsible for delivery of the peptide to portal vessels in the median eminence, and one whose relationship, if any, to hypophysiotropic function is less direct. A dense plexus of rhGRF-stained fibers was found throughout the external lamina of the median eminence that is the route by which the peptide is delivered to the anterior pituitary. This projection appears to arise primarily from a group of rhGRF-immunoreactive neurons centered in the arcuate nucleus. Some 1,000-1,500 rhGRF-positive neurons were counted on each side of the brain in rats pretreated with colchicine. Colocalization studies, using a sequential double staining technique, indicated that a subset of rhGRF-immunoreactive neurons in the arcuate region contain neurotensin immunoreactivity. No evidence was obtained for colocalization of rhGRF with either of two pro-opiomelanocortin-derived peptides (alpha-melanocyte-stimulating hormone, adrenocorticotropic hormone (1-24)) in individual neurons in the arcuate nucleus. Much smaller groups of neurons were localized in the parvicellular division of the paraventricular nucleus of the hypothalamus and in the dorsomedial nucleus, and it is unclear whether they contribute to the plexus of rhGRF-stained fibers in the median eminence. The only other region in the rat brain in which rhGRF-stained cells were found reliably was in the area that roughly encapsulates the caudal aspect of the ventromedial nucleus of the hypothalamus. Because cells in this region are not known to project to the median eminence, they may be assumed to contribute to the extrahypophysiotropic rhGRF-stained projections outlined below. From the level of the arcuate and ventromedial nuclei, rhGRF-immunoreactive fibers could be traced along the base of the brain and through the periventricular system to discrete terminal fields limited almost exclusively to the hypothalamus and adjoining parts of the basal telencephalon. All parts of the periventricular region of the hypothalamus receive an input, including the preoptic and anterior parts in which somatostatin-containing neurons that project to the median eminence are clustered. Other prominent terminal fields were localized in discrete parts of the dorsomedial, paraventricular, suprachiasmatic, and premammillary nuclei, and in the medial preoptic and lateral hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Combined Autoradiographic and Immunohistochemical Evidence for an Association of Somatostatin Binding Sites with Growth Hormone‐Releasing Factor‐Containing Nerve Cell Bodies in the Rat Arcuate Nucleus

“…Interestingly, whereas the former two groups (i.e. arcuate and periventricular) have been shown to project to the median eminence, the latter is currently believed mainly to contribute to extrahypophysiotropic projections to the basal forebrain (8).…”

“…The net result is a striking ultradian rhythm of G H secretion (6). GRF-containing projections to the median eminence originate almost exclusively from nerve cell bodies located in the arcuate nucleus of the hypothalamus (7,8). In contrast, infundibular SRIF-containing axons have been shown to arise from neurons scattered along the lateral wall of the third ventricle in the anterior periventricular nucleus of the hypothalamus (9) from where they reach the median eminence via a lateral arc (10).…”

International Union of Pharmacology. XXXV. The Glucagon Receptor Family

“…GHRH also stimulates growth hormone gene transcription (Barinaga et al, 1983;Gick et al, 1984) and pituitary somatotroph cell proliferation (Billestrup et al, 1986;Mayo et al, 1988). GHRH is released from neurosecretory cells in the arcuate nuclei of the hypothalamus (Merchenthaler et al, 182 1984;Sawchenko et al, 1985) and along with the inhibitory peptide somatostatin mediates the neuroendocrine regulation of pituitary growth hormone synthesis and secretion.…”

Spatiotemporal patterns of secretomotor neuron generation in the parvicellular neuroendocrine system 1Published on the World Wide Web on 3 June 1997. 1

“…44) was provided by Dr. Vale and was used at a concentration of 1:4,000 [51]. The rabbit anti-GRH antiserum (G-75) was provided by Dr. Vale; it was absorbed with human α-globulin and used at a dilution of 1:6,000 [46]. The rabbit anti-SS antiserum, directed against SS 15 -28 , was purchased from Incstar (No.…”