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Spexin (Spx), a novel neuropeptide, composed of 14 amino acid residues, is evolutionally conserved from fish to mammals. It has been suggested that Spx has pleiotropic functions in mammals. However, reports about Spx are very limited. To clarify the roles of Spx in the regulation of reproduction and food-intake in the spotted scat, the spx ( ssspx ) gene was cloned and analyzed. Analysis of the tissue distribution by RT-PCR showed that ssspx expression was widespread. During ovary development, expression of ssspx was found to be highest in phase II, moderate in phase III, and at its lowest level in phase IV. Ssspx expression was significantly down-regulated in the hypothalamus after treatment with E 2 both in vitro and in vivo . A significant increase of ssspx was observed after 2 and 7 days of food deprivation. However, the ssspx transcript levels in the 7 day fasting group decreased significantly after refeeding 3 h after the scheduled feeding time. This suggests that ssSpx may be involved in the regulation of reproduction and food-intake in the spotted scat. [ABSTRACT FROM AUTHOR]

Estrogen receptors (Er) play a critical role in vitellogenesis. Three ers ( erα , erβ1 and erβ2 ) and vitellogenins (v tg-A , v tg-B and v tg-C ) subtypes were isolated in various fish species, while the contribution of each Er to the regulation of vtgs expression was not analyzed in detail. Here, erα , erβ1 and erβ2 were cloned and all were found to be expressed in female liver in Scatophagus argus . During proteic vitellogenesis stage, er α was simultaneously up-regulated, while er β 1 and er β 2 were not, with three vtgs in female liver. The effects of 17β-estradiol (E 2 ) alone or combined with Er antagonists on ers , vtgs mRNA expressions and Vtg protein content in incubated male liver were examined by real-time PCR and enzyme-linked immunosorbent assay (ELISA), respectively. The expressions of erα , erβ1, vtgs mRNA and Vtg protein increased significantly after 24 h incubation with E 2 (0.1, 1 and 10 μM), while Er nonselective antagonist ICI 182 780 (0.01, 0.1 and 1 μM) significantly attenuated the up-regulation effects of E 2 on ers, vtgs mRNA and Vtg protein in a dose-dependent manner. Erα selective antagonist Methyl-piperidinopyrazole (MPP) (0.01, 0.1 and 1 μM) significantly attenuated the up-regulation effects of E 2 on erα , vtg-B , vtg-C mRNA and Vtg protein, while promoted the expression of erβ1 and vtg-A . Erβ selective antagonist Cyclofenil (0.01, 0.1 and 1 μM) attenuated the up-regulation effects of E 2 on erβ1 , erβ2 , vtg-A , vtg-C mRNA and Vtg protein while promoted the expression of erα and vtg-B . Our results suggest that the regulation of Ers on different vtgs was divergent in S. argus . [ABSTRACT FROM AUTHOR]