Regulatory Mechanism Of Reproductive Development And Reproductive Activity Of GnIH In Chicken

Gonadotropin-inhibiting hormone (GnIH) is a polypeptide hormone secreted byhypothalamic, which became a key factor to inhibit reproductive activity of avian (bird)through directly or indirectly regulating GnRH secretion of pituitary. The studies on GnIHcurrently was a hot field of reproductive biology. The regulatory mechanism of GnIH inreproductive development and reproductive activity of chicken were studied in this paper.In experiment1,60healthy roosters were randomly divided into two groups, immunizedgroup and control group, and the former was active-immunized with0.5g GnIH per roosterat60d,80d and100d. The blood LH and T concentration were tested at60d,80d,90,100,120d,150d and200d. The testicular development and gene expression level of GnRH, GnIH,VIP in hypothalamic and LH, PRL in pituitary were checked at90d,120d,150d and200d.The semen quality of trained roosters were checked every three days from185-200d. Theresults showed that the immunization could inhibit the testis development, elevate bloodblood T levels and GnIH mRNA levels, and decreased LH mRNA levels in the reproductivedevelopment of60-120d, with no significant effect on GnRH、VIP、PRL mRNA levels.After sexual maturity, the weight and volume of immunized testicles continued to develop,but the control decreased. the immunized sperm motility and density were higher than thecontrol, although semen volume less than the latter. The blood T, LH and GnIH mRNAlevels of the treated were higher, and LH mRNA level was lower than the control. Therewere no significant differences in GnRH、VIP and PRL mRNA levels between the twogroups.The18healthy roosters of190days were divided into three groups in experiment2.Group P were only treated with1mg GnIH dissolved with30%PVP-K30by intramuscularinjection at d1, group G were injected with1mg GnIH dissolved in saline at d1, d4and d7,and group D were given the same volume saline at the same time. The blood LH, Tconcentrations and semen quality were detected at d1, d4, d7and d10, and the testiculardevelopment and GnRH, GnIH, VIP, LH and PRL gene expression levels were checked atd10. Those results show that the exogenous GnIH could inhibit testicular development, reduce blood LH, T concentrations and semen quality that including semen volume, spermconcentration and sperm motility. For different GnIH dissolution, the testicular volume,weight and sperm motility were significantly larger and the semen volume and density wereslightly lower in group G than group P, but there were no significant difference in blood LHand T levels between group G and P. The exogenous GnIH increased GnRH, GnIH mRNAlevels and reduced LH and PRL mRNA levels, but had no significant effect on VIP mRNAlevels.In experiment3, the18health hens190-days were divided into group P, G and D, withexperimental programs same to experiment2. The results showed that the exogenous GnIHinhibited laying performance and follicular development. The LWF number were lower andSYF number were higher in group D than the other groups, and the LYF number was higherthan group G and lower than group P. The blood P4concentration of group D was higherthan the other two groups, and there were no significant difference in the blood LH and E2level between three groups. The exogenous GnIH increased GnIH, VIP and PRL mRNAlevels, but had no significant effects on GnRH and LH gene expression.