Gonadotrophin-Inhibitory Hormone in the Cichlid Fish Cichlasoma dimerus: Structure, Brain Distribution and Differential Effects on the Secretion of Gonadotrophins and Growth Hormone

DI YORIO, PAULA; PEREZ SIRKIN, DANIELA; DELGADÍN TH; SHIMIZU,A; TSUTSUI K; SOMOZA, GM; VISSIO, PAULA G.

JOURNAL OF NEUROENDOCRINOLOGY.

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017

0953-8194

The role of gonadotrophin-inhibitory hormone (GnIH) in the inhibition of the reproductive axis hasbeen well-established in birds and mammals. However, its role in other vertebrates, such as the tel-eost fish, remains controversial. In this context, the present study aimed to evaluate whether GnIHmodulates the release of gonadotrophins and growth hormone (GH) in the cichlid fish Cichlasomadimerus. First, we partially sequenced the precursor polypeptide for GnIH and identified three puta-tive GnIH peptides. Next, we analysed the expression of this precursor polypeptide via a polymerasechain reaction in the reproductive axis of both sexes. We found a high expression of the polypep-tide in the hypothalamus and gonads of males. Immunocytochemistry allowed the observation ofGnIH-immunoreactive somata in the nucleus posterioris periventricularis and the nucleus olfacto-retinalis, with no differences between the sexes. GnIH-immunoreactive fibres were present in allbrain regions, with a high density in the nucleus lateralis tuberis and at both sides of the thirdventricle. Finally, we performed in vitro studies on intact pituitary cultures to evaluate the effect oftwo doses (106M and 108M) of synthetic C. dimerus (cd-) LPQRFa-1 and LPQRFa-2 onthe release of gonadotrophins and GH. We observed that cd-LPQRFa-1 decreased b-luteinising hor-mone (LH) and b-follicle-stimulating hormone (FSH) and also increased GH release to the culturemedium. The release of b-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 LH and FSH release and stimulates GH release in intact pituitary cultures of C. dimerus. Theresults also show that cd-LPQRF-2 could act as an FSH-releasing factor in this fish species.