Role of nitric oxide in ovarian follicular development and egg production in Japanese quail ( Coturnix coturnix japonica)

Role of nitric oxide (NO) in regulating the reproductive functions at hypothalamo-hypophysealovarian axis in Japanese quail was studied. In first experiment, metabolites of NO, i.e. nitrite and nitrate (NO 2 and NO 3) were estimated together in hypothalamus, serum and ovarian follicles of good and poor layers. In the second experiment, different NO modulators such as l-arginine ( l-Arg), sodium nitroprusside (SNP) and N G-nitro- l-arginine methyl ester, HCl ( l-NAME) were administered to the birds. In the first experiment, significantly higher ( P < 0.01) NO 2 and NO 3 levels in serum, hypothalamus and largest ( F 1) ovarian follicles were observed in good layers as compared to poor layers. Higher ( P < 0.05) NO 2 and NO 3 concentration was observed in F 1 follicles than smaller follicles ( F 2) only in good layers. The NO 2 and NO 3 concentration was significantly reduced ( P < 0.05) in post ovulatory follicles (POFs) in comparison to F 1 and F 2 follicles. In the second experiment, the serum NO 2 and NO 3 concentrations were higher ( P < 0.05) in the SNP, lower ( P < 0.05) in the l-NAME group and unchanged in the l-Arg treated group in comparison to control group. Compared to control, l-Arg and SNP increased ( P < 0.05) the hypothalamic NO 2 and NO 3 concentration where as l-NAME reduced ( P < 0.05) these levels. The NO 2 and NO 3 concentration was increased ( P < 0.05) as the follicle size increased and it was significantly reduced ( P < 0.05) in POFs. The higher ( P < 0.05) follicular NO 2 and NO 3 concentration was observed in l-Arg group in comparison to control group. Egg production was also found to be higher ( P < 0.05) in l-Arg group whereas it was not different ( P > 0.05) in SNP and l-NAME treated groups. The yolk weight and yolk to albumin ratio was reduced ( P < 0.05) in l-NAME group in comparison to control group. It may be concluded from the present study that NO plays a key role in regulating follicular development, ovulatory mechanisms and egg production in Japanese quail.