| The hypothalamus and pituitary were important neuroendocrine organs that secreted a variety of neuropeptides and hormones and participated in the regulation of multiple physiological activities such as reproduction,growth,stress and feeding.Chinese sturgeon was a non-teleost ray-finned fish with a special evolutionary status,but information on the neuroendocrine system was still scarce.Based on the transcriptomic data of the hypothalamus-pituitary axis of Chinese sturgeon,46 hypothalamus neuropeptide genes were identified in this study,which were involved in the regulation of reproduction,growth,stress and feeding,respectively.In addition,six pituitary hormone genes were identified in this study,including reproductive hormones: follicle-stimulating homone(FSH)and luteinizing hormone(LH),growth-related hormones: growth hormone(GH)/prolactin(PRL)/somatolactin(SL),and stress-related hormone gene: proopiomelanocortin(POMC).Similar to teleost,immunostaining localization analysis of the pituitary of Chinese sturgeon showed that LH and FSH were located in the meso-adenohypophysis,SL was located in the pro-adenohypophysis,and POMC was located in the pro-adenohypophysis and metaadenohypophysis.Tachykinins belonged to a large,evolutionarily conserved family of brain/gut peptides that were involved in a variety of physiological functions in mammals,such as reproductive regulation.However,little information was available about tachykinins in ancient fish lineage.In the present study,we firstly isolated three tachykinin genes(named tac1,tac3 and tac4)and three neurokinin receptors(named nk1 r,nk2r and nk3r)from Chinese sturgeon brain and pituitary.Sequence analysis showed that tac1 encoded substance P(SP)and neurokinin A(NKA),tac3 encoded neurokinin B(NKB)and NKB-related peptide(NKBRP),and tac4 encoded hemokin 1(HK-1)and hemokin 2(HK-2),respectively.Tissue expression analysis showed that the three tac genes were highly detected in the telencephalon and hypothalamus,whereas nkr genes were widely expressed in peripheral tissues.Spatio-temporal expression analysis showed that all three tac genes were highly expressed in unknown sex individuals.Intraperitoneal injection experiments showed that both as SP and as NKB could stimulate luteinizing hormone(LH)secretion in Chinese sturgeon serum.At the transcriptional level,as SP and as NKB could significantly reduce pituitary follicle-stimulating hormone beta(fshβ)m RNA expression,but induce pituitary growth hormone(gh)m RNA expression.In addition,estradiol(E2)could stimulate tac3 m RNA expression in the hypothalamus.In conclusion,this study will enrich the information on the neuroendocrine system of Chinese sturgeon,while providing basic knowledge on the tachykinin family of Chinese sturgeon,suggesting that as NKB and as SP were involved in reproductive and growth related functions on pituitary. |
