[Frontiers in Bioscience 2, d88-125, March 1, 1997]
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CROSS-TALK SIGNALS IN THE CNS: ROLE OF NEUROTROPHIC AND HORMONAL FACTORS, ADHESION MOLECULES AND INTERCELLULAR SIGNALING AGENTS IN LUTEINIZING HORMONE-RELEASING HORMONE (LHRH)-ASTROGLIAL INTERACTIVE NETWORK

Bianca Marchetti

Department of Pharmacology, Medical School, University of Catania, 95125 Catania, Laboratory of Biotech. Neuropharmacology, OASI Institute for Research and Care (IRCCS) on Mental Retardation and Brain Aging (IRCCS) Troina, (EN), Italy.

Received 8/2/96; Accepted 2/20/97; On-line 3/1/97

8. LHRH Neuron-Astroglia Interactions during Development

During embryonic development, the LHRH neuronal system appears to be unique among all neuropeptide expressing genes in the central nervous system (CNS), to make a migration pathway from the epithelium of the medial olfactory placode into the developing basal forebrain (202-208). Failure of LHRH neuronal migration is responsible for the suppression of the pituitary-gonadal axis in Kallmann's syndrome (209), an inherited migration disorder resulting in hypogonadotropic hypogonadism with anosmia (203-206, 210). The migration of LHRH neurons is in close association with a neural cell adhesion molecule, N-CAM and Ng-CAM enriched fiber bundle (211, 212). In mice (203), monkeys (212) and chicks (207, 208), LHRH is expressed in neurons early in development and continue to be expressed in neurons as they migrate. Vomeronasal nerves have been included as part of a complex of olfactory fibers that participate in LHRH cell migration (205, 206, 213-214). The exact mechanism(s), however, involved in LHRH neuronal migration remain unclear. The fibers associated with LHRH neuronal migration have been demonstrated to express the neural cell adhesion molecule, N-CAM (204, 211), a highly polysialated form of neural cell adhesion molecule, PSA-N-CAM (214), peripherin (213) and the CC2-immunoreactive olfactory glycoconiugate (216). Recently, Yoshida et al. (217) have shown that LHRH neurons migration across the medial olfactory bulb and forebrain is associated with a caudal branch of the vomeronasal nerve. After migration in the forebrain in association with the TAG1+, PSA/N-CAM+ axons, the majority of LHRH neurons continue to migrate laterally and ventrally into the preoptic area/anterior hypothalamus (217) . It seems highly possible that other factors such as soluble chemotropic molecules, extracellular matrix molecules, and adjacent neurons and glial cells, may also be involved in this phenomenon.