The Daily Expression Profile of Neuropeptides ( gnih, gnrh3, kiss1 and kiss2 ):A Study of Possible Interaction in the Brain of Zebrafish ( Danio rerio )

Involvement of neuropeptides in the reproduction of fish (seasonal/regular) is known. The daily rhythmicity and their possible interaction of four major neuropeptides namely gnih , gonadotropin-inhibitory hormone; gnrh, gonadotropinreleasing hormone; kiss1/2, kisspeptin 1/2; is not known to any fish. Our present study on the whole brain of zebrafish (Danio rerio) aimed at the daily rhythmicity of the mRNA expression of these four neuropeptides in a 12 h light/12 h dark photoperiod (LD). Only kiss2 in its expression gives a rhythmicity but other three peptides are not rhythmic. Moreover, the expression of gnih is 10-fold lower than gnrh3. Our STRING network analysis suggests kiss2 act as the mediator to communicate with gnih , gnrh3, and kiss1. Our present finding is indicating the important role of kiss2 in mediating the reproductive signal and may play a central role in the synchronization of the environmental signal and reproductive periodicity.