Novel pituitary actions of NKB for anorectic peptides regulation in grass carp

Abstract

Neurokinin B (NKB), the gene product of tachykinin 3 (TAC3), has recently emerged as a key regulator for reproduction. However, previous studies were mainly focused on the functions of NKB on hypothalamus GnRH regulation in mammals, little information is available regarding its functional role at the pituitary level in teleost. In this study, using grass carp pituitary cells as model, transcriptome analysis revealed that the differential expression genes (DEGS) induced by NKBa were mainly involved in the regulation of appetite, hormone activity, growth factor, and metabolic process. Secondly, by using qPCR, we further confirmed that NKB could significantly induce four anorectic peptides (UTS1, CART, POMCb and NMB) mRNA expression in a time- and dose-dependent manner in grass carp pituitary cells. Thirdly, using a pharmacological approach, the stimulatory effects of NKBa on pituitary UTS1, CART, POMCb and NMB mRNA expression were found to be all mediated by NK3R and coupled to the cAMP/PKA, PLC/IP3/PKC and Ca2+/CaM/CaMK-II signal pathways. Furthermore, intraperitoneal injection of NKBa could also significantly induce the four anorectic peptides (UTS1, CART, POMCb and NMB) mRNA expression in grass carp pituitary. Finally, we found that food intake in grass carp could significantly induce hypothalamus TAC3a and TAC3b mRNA expression. These results, taken together, suggested that NKB should be a satiety factor and involved in the regulation of pituitary anorectic peptides in teleost.