title: Gonadotrophin-Inhibitory Hormone in the Cichlid Fish Cichlasoma dimerus: Structure, Brain Distribution and Differential Effects on the Secretion of Gonadotrophins and Growth Hormone.
abstract: The role of gonadotrophin-inhibitory hormone (GnIH) in the inhibition of the reproductive axis has been well-established in birds and mammals. However, its role in other vertebrates, such as the teleost fish, remains controversial. In this context, the present study aimed to evaluate whether GnIH modulates the release of gonadotrophins and growth hormone (GH) in the cichlid fish Cichlasoma dimerus. First, we partially sequenced the precursor polypeptide for GnIH and identified three putative GnIH peptides. Next, we analysed the expression of this precursor polypeptide via a polymerase chain reaction in the reproductive axis of both sexes. We found a high expression of the polypeptide in the hypothalamus and gonads of males. Immunocytochemistry allowed the observation of GnIH-immunoreactive somata in the nucleus posterioris periventricularis and the nucleus olfacto-retinalis, with no differences between the sexes. GnIH-immunoreactive fibres were present in all brain regions, with a high density in the nucleus lateralis tuberis and at both sides of the third ventricle. Finally, we performed in vitro studies on intact pituitary cultures to evaluate the effect of two doses (10(-6)  m and 10(-8)  m) of synthetic C. dimerus (cd-) LPQRFa-1 and LPQRFa-2 on the release of gonadotrophins and GH. We observed that cd-LPQRFa-1 decreased β-luteinising hormone (LH) and β-follicle-stimulating hormone (FSH) and also increased GH release to the culture medium. The release of β-FSH was increased only when it was stimulated with the higher cd-LPQRFa-2 dose. The results of the present study indicate that cd-LPQRFa-1, the cichlid fish GnIH, inhibits β-LH and β-FSH release and stimulates GH release in intact pituitary cultures of C. dimerus. The results also show that cd-LPQRF-2 could act as an β-FSH-releasing factor in this fish species.
authors.affiliation: Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, DBBE, FCEN-UBA/IBBEA-CONICET-UBA, Ciudad Universitaria, (C1428EHA), Buenos Aires, Argentina.
authors.forename: M P
authors.initials: MP
authors.lastname: Di Yorio
authors.affiliation: Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, DBBE, FCEN-UBA/IBBEA-CONICET-UBA, Ciudad Universitaria, (C1428EHA), Buenos Aires, Argentina.
authors.forename: D I
authors.initials: DI
authors.lastname: Pérez Sirkin
authors.affiliation: Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, DBBE, FCEN-UBA/IBBEA-CONICET-UBA, Ciudad Universitaria, (C1428EHA), Buenos Aires, Argentina.
authors.forename: T H
authors.initials: TH
authors.lastname: Delgadin
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Shimizu
authors.affiliation: Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tsutsui
authors.affiliation: Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH), CONICET-UNSAM, Chascomús, Buenos Aires, Argentina.
authors.forename: G M
authors.initials: GM
authors.lastname: Somoza
authors.affiliation: Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, DBBE, FCEN-UBA/IBBEA-CONICET-UBA, Ciudad Universitaria, (C1428EHA), Buenos Aires, Argentina.
authors.forename: P G
authors.initials: PG
authors.lastname: Vissio
mesh_terms: D000818:Animals; D023681:Cichlids / Q000235:genetics / Q000378:metabolism*; D005260:Female; D029941:Fish Proteins / Q000378:metabolism*; D037201:Follicle Stimulating Hormone, beta Subunit / Q000378:metabolism; D006062:Gonadotropins / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D036361:Peptide Hormones / Q000008:administration & dosage; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D037201:Follicle Stimulating Hormone, beta Subunit; D006062:Gonadotropins; D007028:Hypothalamic Hormones; D036361:Peptide Hormones; D012333:RNA, Messenger; D013006:Growth Hormone
keywords: fish; follicle-stimulating hormone; gonadotrophin-inhibitory hormone; growth hormone; luteinising hormone