Interactions of gonadotropin-releasing hormone (GnRH) and gonadotropin-inhibitory hormone (GnIH) in birds and mammals.
Gonadotropin-releasing hormone (GnRH) regulates secretion of both of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone. Thus, it is a key hormone for vertebrate reproduction. GnRH was considered to be unusual among hypothalamic neuropeptides in that it appeared to have no direct antagonist, although some neurochemicals and peripheral hormones (opiates, GABA, gonadal steroids, inhibin) can modulate gonadotropin release to a degree. Five years ago, a vertebrate hypothalamic neuropeptide that inhibited pituitary gonadotropin release in a dose-dependent manner was discovered in quail by Tsutsui et al. (2000. Biochem Biophys Res Commun 275:661-667). We now know that this inhibitory peptide, named gonadotropin-inhibitory hormone, or GnIH, is a regulator of gonadotropin release in vitro and in vivo. Its discovery has opened the door to an entirely new line of research within the realm of reproductive biology. In our collaborative studies, we have begun to elucidate the manner in which GnIH interacts with GnRH to time release of gonadotropins and thus time reproductive activity in birds and mammals. This paper reviews the distribution of GnIH in songbirds relative to GnRHs, and our findings on its modes of action in vitro and in vivo, based on laboratory and field studies. These data are simultaneously compared with our findings in mammals, highlighting how the use of different model species within different vertebrate classes can be a useful approach to identify the conserved actions of this novel neuropeptide, along with its potential importance to vertebrate reproduction.
Bentley
George E
GE
Department of Integrative Biology, University of California, Berkeley, California 94720, USA. gb7@berkely.edu
Kriegsfeld
Lance J
LJ
Osugi
Tomohiro
T
Ukena
Kazuyoshi
K
O'Brien
Sara
S
Perfito
Nicole
N
Moore
Ignacio T
IT
Tsutsui
Kazuyoshi
K
Wingfield
John C
JC
D000818:Animals; D030161:Avian Proteins / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D006224:Cricetinae / Q000502:physiology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000378:metabolism; D008297:Male; D008322:Mammals / Q000378:metabolism* / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D020308:Songbirds / Q000378:metabolism* / Q000502:physiology
D030161:Avian Proteins; D007028:Hypothalamic Hormones; C413752:gonadotropin-inhibitory hormone, Coturnix japonica; D007987:Gonadotropin-Releasing Hormone