Gonadotropin inhibitory hormone (GnIH) a link between feeding and reproduction in the ciclid fish Cichlasoma dimerus

MARÍA PAULA DI YORIO; DANIELA PEREZ-SIRKIN; TOMAS H. DELGADIN; JULIETA E. SALLEMI; KAZUYOSHI TSUTSUI; GUSTAVO M. SOMOZA; PAULA G. VISSIO

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias.; 2017

GnIH downregulates reproductive function in vertebrates. Moreover, there are reports that propose that GnIH acts as an orexigenic peptide in birds and mammals. Previously, we characterized Cichlasoma dimerus? GnRH variants (sGnRH, sbGnRH, cGnRH), the orexigenic peptide Neuropeptide Y (NPY) and GnIH peptide, and demonstrated that GnIH inhibited gonadotropin but stimulated growth hormone release in adults of this specie. The general objective was to start studying GnIH as a link between feeding and reproduction in C. dimerus. We evaluate possible morphological relationships between neurons and fbers of GnIH, GnRH variants and NPY, and we analyze variations in the expression of thosepeptides in animals after fasting. By double label confocal immunofluorescences, we found that neurons of the nucleus olfacto retinalis (NOR) co-expressed GnIH and sGnRH, and that some fbers co-expressed both peptides while others were immunoreactive (-ir) to each one at hypothalamic level. There were no contacts between sbGnRH or cGnRH fbers with GnIH neurons in the NOR. GnIH-ir neurons of the hypothalamus did not co-express any GnRH variant. GnIH-ir fbers were observed in close proximity to NPY-ir fbers at hypothalamic level and few contacts between cGnRH-ir and GnIH-ir fbers were observed in midbrain. On the other hand, animals were isolated in aquaria and daily fed at a fx time. After an adaptation period, they were randomly assigned to feeding or fasting groups.Four weeks later, variations in mRNA levels of those peptides were determined by real time PCR in telencephalon, hypothalamus and medium-posterior brain. Fasting conditions induced a signifcant decrease in GnIH mRNA levels (p=0.0375) in the hypothalamus, a clear tendency of decreasing in NPY expression but no changes for GnRH variants in telencephalon and medium-posterior brain. Taking into account our results, we proposed that GnIH could act as a link between feeding status and reproduction in C. dimerus.