title: Neurotrophic effects of BDNF on embryonic gonadotropin-releasing hormone (GnRH) neurons.
abstract: Secretion of gonadotropin-releasing hormone (GnRH) at the median eminence is the essential activator of the reproductive axis. The mechanisms by which embryonic GnRH neurons migrate from the olfactory placode to the preoptic area and then elaborate neurites that course through the hypothalamus to terminate at the median eminence are largely unknown. We investigated the hypothesis that GnRH neurite outgrowth is promoted by brain-derived neurotrophic factor (BDNF) because GnRH neurites course through BDNF-rich areas of the forebrain during their development. Confocal microscopy revealed that most (86%) cultured embryonic GnRH cells tagged with a green fluorescent protein reporter were immunoreactive for TrkB. In primary cultures of E12.5 olfactory tissue, treatment with BDNF induced a dose-dependent increase in neurite outgrowth, but had no discernible effect on branching. BDNF induced phosphorylation of Ca(2+)/cAMP response element-binding protein (pCREB) in both GnRH and non-GnRH cells in these cultures. This was not associated with phosphorylation of ERK in GnRH-immunoreactive cells, though BDNF treatment did stimulate pERK in neighbouring non-GnRH cells. Promotion of neurite outgrowth is unlikely therefore to result from activation of the Ras-MAPK/ERK pathway. We conclude that the developing GnRH secretory system is directly sensitive to BDNF and that this polypeptide functions as a neurotrophic factor for GnRH neurons.
authors.affiliation: Department of Anatomy, University of Cambridge, Cambridge, UK.
authors.forename: Anna S
authors.initials: AS
authors.lastname: Cronin
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Horan
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Spergel
authors.forename: A Nigel
authors.initials: AN
authors.lastname: Brooks
authors.forename: Michael H
authors.initials: MH
authors.lastname: Hastings
authors.forename: Francis J P
authors.initials: FJ
authors.lastname: Ebling
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology* / Q000196:embryology; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002452:Cell Count / Q000379:methods; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004622:Embryo, Mammalian; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D007124:Immunoenzyme Techniques / Q000379:methods; D007150:Immunohistochemistry / Q000379:methods; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D020813:Receptor, trkB / Q000378:metabolism
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D017362:Cyclic AMP Response Element-Binding Protein; D008164:Luminescent Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone; D011189:Potassium Chloride; D020813:Receptor, trkB; D020928:Mitogen-Activated Protein Kinases