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Expression of GnRH genes is elevated in discrete brain loci of chum salmon before initiation of homing behavior and during spawning migration

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Title: Expression of GnRH genes is elevated in discrete brain loci of chum salmon before initiation of homing behavior and during spawning migration
Authors: Onuma, Takeshi A. Browse this author
Makino, Keita Browse this author
Ando, Hironori Browse this author
Ban, Masatoshi Browse this author
Fukuwaka, Masa-aki Browse this author
Azumaya, Tomonori Browse this author
Urano, Akihisa Browse this author
Keywords: Spawning migration
Chum salmon
Gonadotropin-releasing hormone
Brain
Gonad
Pituitary-gonadal axis
Behavior
Issue Date: 15-Sep-2010
Publisher: Elsevier
Journal Title: General and Comparative Endocrinology
Volume: 168
Issue: 3
Start Page: 356
End Page: 368
Publisher DOI: 10.1016/j.ygcen.2010.05.001
Abstract: Our previous studies suggested the importance of gonadotropin-releasing hormones (GnRHs) for initiation of spawning migration of chum salmon, although supporting evidence had been not available from oceanic fish. In farmed masu salmon, the amounts of salmon GnRH (sGnRH) mRNAs in the forebrain increased in the pre-pubertal stage from winter through spring, followed by a decrease toward summer. We thus hypothesized that gene expression for GnRHs in oceanic chum salmon changes similarly, and examined this hypothesis using brain samples from winter chum salmon in the Gulf of Alaska and summer fish in the Bering Sea. They were classified into sexually immature and maturing adults, which had maturing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GnRH mRNAs were determined by real-time PCRs. The amounts of sGnRH mRNA in the maturing winter adults were significantly larger than those in the maturing summer adults. The amounts of sGnRH and chicken cGnRH-II mRNAs then peaked during upstream migration from the coast to the natal hatchery. Such changes were observed in various brain loci including the olfactory bulb, terminal nerve, ventral telencephalon, nucleus preopticus parvocellularis anterioris, nucleus preopticus magnocellularis and midbrain tegmentum. These results suggest that sGnRH neurons change their activity for gonadal maturation prior to initiation of homing behavior from the Bering Sea. The present study provides the first evidence to support a possible involvement of neuropeptides in the onset of spawning migration.
Type: article (author version)
URI: http://hdl.handle.net/2115/43854
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 浦野 明央

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