title: Distribution of gonadotropin releasing-hormone-II in the house sparrow brain (Passer domesticus).
abstract: In songbirds, three isoforms of gonadotropin-releasing hormone (GnRH) have been reported: chicken GnRH-I (GnRH-I); and -II (GnRH-II); and lamprey GnRH-III (lGnRH-III). In galliformes, the distribution of GnRH-I and -II have been extensively studied. GnRH-I cell bodies are located primarily in the preoptic-septal region and primarily project to the median eminence. GnRH-II cell bodies are located in the midbrain and project to various hypothalamic and extrahypothalamic regions. In songbirds, the distributions of only GnRH-I and lGnRH-III have been thoroughly described. Songbirds differ from galliformes in that they possess specialized neural regions for the learning and production of complex vocalizations, the song-control system. In songbirds lGnRH-III was found within many song nuclei. In this study, we investigated the distribution of GnRH-II in the male house sparrow (Passer domesticus) brain. Our objectives were (1) to determine the distribution of GnRH-II in the male songbird brain and (2) to investigate the presence of GnRH-II in song control nuclei. Our study identified immunoreactive magnocellular GnRH-II cell bodies in the oculomotor region of the mesencephalon and parvicellular cells in the lateral hypothalamus. Also, an extensive network of GnRH-II immunoreactive fibres was observed in hypothalamic nuclei and extrahypothalamic regions. Immunoreactive GnRH-II fibres were most abundant in the preoptic area, ventromedial nucleus, hippocampus and the medial septum. Sparse immunoreactivity was also observed in the mesencephalon and diencephalon. GnRH-II was not identified in any of the song-control nuclei. Unlike lGnRH-III, these data suggest that GnRH-II is not directly involved with song learning, perception or production.
authors.affiliation: Graduate Program in Neuroscience, University of Western Ontario, London, Ont., Canada N6A 5C2. tjsteven@uwo.ca
authors.forename: Tyler J
authors.initials: TJ
authors.lastname: Stevenson
authors.forename: Lutgarde
authors.initials: L
authors.lastname: Arckens
authors.forename: Scott A
authors.initials: SA
authors.lastname: MacDougall-Shackleton
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D001931:Brain Mapping; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D046370:Sparrows / Q000033:anatomy & histology / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D007987:Gonadotropin-Releasing Hormone; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-