Identification of gonadotropin-inhibitory hormone in the zebra finch (Taeniopygia guttata): Peptide isolation
 cDNA cloning and brain distribution

Yasuko Tobari
Norio Iijima
Kenta Tsunekawa
Tomohiro Osugi
Kazuo Okanoya
Kazuyoshi Tsutsui
Hitoshi Ozawa

Two novel RFamide peptides
 kisspeptins and gonadotropin-inhibitory hormone (GnIH) are neuropeptides that appear critical in the regulation of the reproductive neuroendocrine axis. GnIH was first identified in avian brain
 however
 kisspeptins have not been identified in birds. To determine biochemically the presence of kisspeptins and GnIH in the zebra finch
 a study was conducted to isolate these two peptides from zebra finch brain. Peptides were isolated by immunoaffinity purification and only one peptide was characterized by mass spectrometry. This peptide was confirmed to be a 12-amino acid sequence with RFamide at its C-terminus its sequence is SIKPFSNLPLRFamide (zebra finch GnIH). By this approach
 however
 identification of kisspeptin from zebra finch brain was not achieved. Cloned zebra finch GnIH precursor cDNA encoded three peptides that possess characteristic LPXRFamide (X = L or Q) motifs at the C-termini. In situ hybridization and immunohistochemical analysis revealed the cellular localization of zebra finch GnIH mRNA and peptide in the paraventricular nucleus and the dorsomedial nucleus of the hypothalamus. Fluorescent immunohistochemistry with confocal microscopy indicated that GnIH-immunoreactive (ir) fibers are very close appositions with gonadotropin-releasing hormone-I (GnRH-I) cells. Furthermore GnIH-ir nerve fibers were widely distributed in the multiple brain regions including the septum
 preoptic area
 median eminence
 optic tectum and median eminence. The prominent fibers were seen in the ventral tegmental area
 midbrain central gray and dorsal motor nucleus of the vagus in the medulla. Thus
 GnIH may participate in not only neuroendocrine functions but also regulation of motivation for social behavior and autonomic mechanisms. c 2010 Elsevier Inc.

Peptides

31

5

10.1016/j.peptides.2010.01.015

https://doi.org/10.1016/j.peptides.2010.01.015
https://www.ncbi.nlm.nih.gov/pubmed/20138947
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