"Ontogeny of Gonadotropin-Inhibitory Hormone (GnIH) in the cichlid fish Cichlasoma dimerus."

DI YORIO, MP; SALLEMI JULIETA; TOLEDO SOLIS FJ; PEREZ SIRKIN, DI; DELGADÍN TH; TSUTSUI K; VISSIO, PG

JOURNAL OF NEUROENDOCRINOLOGY.

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018

0953-8194

RFamide peptides are expressed in the early stages of development in most vertebrates. Gonadotropin33inhibitory hormone (GnIH) belongs to the RFamide family, and its role in reproduction has been widely34 studied in adult vertebrates, ranging from fish to mammals. As only three reports evaluated GnIH during35 development, the aim of this study was to characterise the ontogeny of GnIH in a fish model, Cichlasoma36 dimerus. We detected the presence of two GnIH-immunoreactive (GnIH-ir) cell clusters with spatial and37 temporal differences. One cluster was observed by 3 days post-hatching (dph) in the nucleus olfacto38retinalis (NOR) and the other in the nucleus posterioris periventricularis by 14 dph. The number of39 GnIH-ir neurons increased in both nuclei, whereas their size increased only in the NOR from hatchling to40 juvenile stages. These changes occurred from the moment larvae started feeding exogenously and during41 development and differentiation of gonadal primordia. We showed by double-label immunofluorescence42 that only GnIH-ir neurons in the NOR co-expressed GnRH3 associated peptide. In addition, GnIH-ir fibre43 density increased in all brain regions from 5 dph. GnIH-ir fibres were also detected in the retina, optic44 tract and optic tectum, suggesting that GnIH acts as a neuromodulator of photoreception and the45 integration of different sensory modalities. Also, there were GnIH-ir fibres in the pituitary from 14 dph,46 which were in close association with somatotropes. Moreover, GnIH-ir fibres were observed in the saccus47 vasculosus from 30 dph, suggesting a potential role of GnIH in the modulation of its function. Finally, we48 found that gnih was expressed from 1 dph, and that the pattern of variation of its transcript levels was in49 accordance with that of cell number. Present results are the starting point for the study of new GnIH roles50 during development.