title: Identification, expression, and physiological functions of Siberian hamster gonadotropin-inhibitory hormone.
abstract: Gonadotropin-inhibitory hormone (GnIH) is a hypothalamic neuropeptide that inhibits gonadotropin secretion in birds and mammals. To further understand its physiological roles in mammalian reproduction, we identified its precursor cDNA and endogenous mature peptides in the Siberian hamster brain. The Siberian hamster GnIH precursor cDNA encoded two RFamide-related peptide (RFRP) sequences. SPAPANKVPHSAANLPLRF-NH(2) (Siberian hamster RFRP-1) and TLSRVPSLPQRF-NH(2) (Siberian hamster RFRP-3) were confirmed as mature endogenous peptides by mass spectrometry from brain samples purified by immunoaffinity chromatography. GnIH mRNA expression was higher in long days (LD) compared with short days (SD). GnIH mRNA was also highly expressed in SD plus pinealectomized animals, whereas expression was suppressed by melatonin, a nocturnal pineal hormone, administration. GnIH-immunoreactive (-ir) neurons were localized to the dorsomedial region of the hypothalamus, and GnIH-ir fibers projected to hypothalamic and limbic structures. The density of GnIH-ir perikarya and fibers were higher in LD and SD plus pinealectomized hamsters than in LD plus melatonin or SD animals. The percentage of GnRH neurons receiving close appositions from GnIH-ir fiber terminals was also higher in LD than SD, and GnIH receptor was expressed in GnRH-ir neurons. Finally, central administration of hamster RFRP-1 or RFRP-3 inhibited LH release 5 and 30 min after administration in LD. In sharp contrast, both peptides stimulated LH release 30 min after administration in SD. These results suggest that GnIH peptides fine tune LH levels via its receptor expressed in GnRH-ir neurons in an opposing fashion across the seasons in Siberian hamsters.
authors: Department of Biology, Waseda University, and Center for Medical Life Science of Waseda University, 162-8480, Tokyo, Japan.
authors: Takayoshi
authors: T
authors: Ubuka
authors: Kazuhiko
authors: K
authors: Inoue
authors: Yujiro
authors: Y
authors: Fukuda
authors: Takanobu
authors: T
authors: Mizuno
authors: Kazuyoshi
authors: K
authors: Ukena
authors: Lance J
authors: LJ
authors: Kriegsfeld
authors: Kazuyoshi
authors: K
authors: Tsutsui
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D006023:Glycoproteins / Q000235:genetics* / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology; D007028:Hypothalamic Hormones / Q000235:genetics* / Q000502:physiology*; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D017111:Phodopus / Q000235:genetics* / Q000502:physiology*; D017440:Photoperiod; D010870:Pineal Gland / Q000502:physiology; D011301:Preoptic Area / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D006023:Glycoproteins; D007028:Hypothalamic Hormones; D009479:Neuropeptides; C416987:RFamide peptide; D012333:RNA, Messenger; C014995:gonadotropin inhibitor; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D008550:Melatonin