title: Evidence for a novel gonadotropin-releasing hormone in hypothalamic and forebrain areas in songbirds.
abstract: One or more of three distinct forms of gonadotropin-releasing hormones (GnRHs), has been found in all vertebrates studied. Birds are known to contain two types of GnRH, chicken GnRH-I and -II (cGnRH-I and -II), but to date nobody has investigated the possibility of the presence of lamprey GnRH-III in birds. Thus, our objective was to investigate the presence and distribution of immunoreactive lamprey (ir-lamprey) GnRH-III in hypothalamic and forebrain areas in house sparrows (Passer domesticus) and Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii). In addition to its distribution in the CNS, we investigated whether or not exogenous lamprey GnRH-III peptide could elicit luteinizing hormone (LH) release in vivo. This study presents two novel findings: 1) The widespread presence in the central nervous system of an immunoreactive third GnRH in birds that is clearly hypophysiotropic and has gonadotropin-releasing capabilities. Intravenous injection of 100 ng lamprey-GnRH-III peptide elicited a rapid rise in circulating luteinizing hormone as compared to controls. This third GnRH, ir-lamprey GnRH-III, likely has multiple functions, as suggested by its widespread distribution. 2) Ir-lamprey GnRH-III is present in abundance in telencephalic areas, including the hippocampal formation and the song control system. In no vertebrate has a GnRH been localized in these 'higher' control regions before. The fact that ir-lamprey-GnRH-III is present in auditory processing areas (higher vocal center, or HVc, area X, caudomedial neostriatum) and song-producing areas (HVc, robust nucleus of the neostriatum, or RA) suggests a direct way in which auditory processing and song production can affect circulating gonadotropins.
authors.affiliation: Department of Biology, University of Washington, Seattle, WA 98195, USA. gb7@u.washington.edu
authors.forename: George E
authors.initials: GE
authors.lastname: Bentley
authors.forename: Ignacio T
authors.initials: IT
authors.lastname: Moore
authors.forename: Stacia A
authors.initials: SA
authors.lastname: Sower
authors.forename: John C
authors.initials: JC
authors.lastname: Wingfield
mesh_terms: D000818:Animals; D002645:Chickens; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000145:classification / Q000378:metabolism*; D007031:Hypothalamus / Q000033:anatomy & histology / Q000378:metabolism; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009842:Oligopeptides / Q000145:classification / Q000378:metabolism*; D016548:Prosencephalon / Q000033:anatomy & histology / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D020308:Songbirds / Q000033:anatomy & histology / Q000378:metabolism*; D013045:Species Specificity; D014018:Tissue Distribution; D014828:Vocalization, Animal / Q000502:physiology*
chemical_list: D009842:Oligopeptides; C448022:gonadotropin-releasing hormone-III; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D011761:Pyrrolidonecarboxylic Acid