Characterization of the gonadotropin-releasing hormone system in the Neotropical teleost, Steindachneridion parahybae during the annual reproductive cycle in captivity

HONJI, R.; GUIMARAES MOREIRA, R.; LO NOSTRO, F.; CANEPPELE, D

GENERAL AND COMPARATIVE ENDOCRINOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2019 vol. 273 p. 73 - 85

0016-6480

This study evaluated the distribution of two distinct gonadotropin-releasing hormones (GnRHs), corresponding tocatfish GnRH (cfGnRH or GnRH1) and chicken-II GnRH (cGnRH-II or GnRH2), in Steindachneridion parahybaefemales in captivity, focusing this analysis on the reproductive cycle. Further, we found that the GnRH neuronalsystems co-localized with their respective GnRH-associated peptides (GAPs). A group of neurons immunoreactive (ir)to GnRH1 were identified along the ventral region of the olfactory bulb (vOB) in the telencephalon (vTel) and in themain areas of the diencephalon (especially the medial basal hypothalamus, HBM), including fibers extending into thepituitary gland. In contrast, GnRH2 neurons were confined to the midbrain tegmentum, close to the ventricular surface,without projections to the pituitary gland. Moreover, a cfGAP (GnRH1)-specific band (9 kDa) was identified in the brainand pituitary gland, while a cGAP-II (GnRH2)-specific band (26 kDa) was observed only in the brain extract. During thereproductive cycle, GnRH1-ir presented greater optical density values at the vitellogenic and regression stages than atthe previtellogenic stage and after artificially induced to spawn. Larger GnRH2-ir neurons were observed during thereproductive cycle, but a higher optical density was identified only in the regression stage compared with the othermaturation stages. Finally, GnRH1 axons were found to be directed towards the pituitary, with functions ingonadotropin modulation, suggesting that alteration of the synthetic pathways for this GnRH type can contribute to thereproductive dysfunction that occurs in S. parahybae females in captivity, whereas GnRH2 may act as aneuromodulator and/or neurotransmitter.