Gonadotropin-inhibitory hormone in the cichlid fish Cichlasoma dimerus: structure, brain distribution and differential effects on the secretion of gonadotropins and growth hormone.

MARÍA P. DI YORIO; AKIO SHIMIZU; PAULA G. VISSIO; TOMÁS H. DELGADIN; GUSTAVO M. SOMOZA; TOMÁS H. DELGADIN; GUSTAVO M. SOMOZA; DANIELA I. PÉREZ SIRKIN; KAZUYOSHI TSUTSUI; DANIELA I. PÉREZ SIRKIN; KAZUYOSHI TSUTSUI; MARÍA P. DI YORIO; AKIO SHIMIZU; PAULA G. VISSIO

JOURNAL OF NEUROENDOCRINOLOGY.

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 28

0953-8194

The role of gonadotropin-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 teleost fish remains controversial. In this context, the aim of this study was to evaluate whether GnIH modulates the release of gonadotropins 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 and then analysed the expression of this precursor polypeptide by PCR in the reproductive axis of both sexes. We found high expression of the polypeptide in the hypothalamus and gonads of males. Immunocytochemistry allowed observing GnIH-immunoreactive somata in the nucleus posterioris periventricularis (NPPv) and in the nucleus olfacto-retinalis (NOR), with no differences between the sexes. GnIH-immunoreactive fibres were present in all brain regions, with high density in the nucleus lateralis tuberis (NLT) 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 gonadotropins and GH. We observed that cd-LPQRFa-1 decreased β-luteinizing hormone (LH) and β-follicle-stimulating hormone (FSH), and 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. Our results 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 and that cd-LPQRF-2 could act as an FSH releasing factor in this fish species.