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KMID : 1161519990030010001
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Animal Cells and Systems
1999 Volume.3 No. 1 p.1 ~ p.7
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Multiple gonadotropin-releasing hormone neuronal systems in vertebrates
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Parhar Ishwar S.
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Abstract
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Gonadotropin?releasing hormone (GnRH) was originally isolated as a hypo?thalamic peptide that regulates reproduction by stimulating the release of gonadotropins. Using comparative animal models has led to the discovery that GnRH has a more ancient evolutionary origin. During evolution, GnRH peptide underwent gene duplication and structural changes to give rise to multiple molecular forms of GnRHs. Mammalian GnRH initially considered to be the sole molecular form, is now grouped as a family of peptides along with GnRH variants determined from representatives in all classes of vertebrates. Vertebrate species, including primates and humans have more than one GnRH variant in individual brains; a unique GnRH form in the forebrain and chicken II GnRH in the midbrain. Furthermore, several species of bony fish have three molecular variants of GnRH: salmon GnRH, sea?bream GnRH and chicken II GnRH. Also, it has been shown that in addition to the olfactory placodes and the midbrain, there is a third embryonic source of GnRH neurons from the basal diencephalon in birds and fish, which might be true for other vertebrates. Therefore, comparative animal models like fish with discrete sites of expression of three molecular variants of GnRH in individual brains, could provide insight into novel functions of GnRH variants, conservation of gene regulation, and mechanisms governing reproduction in vertebrates
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KEYWORD
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LHRH, Terminal nerve, Midbrain, Preoptic area, Ontogeny
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