Despite its crucial role in the regulation of the sleep-wake cycle and seasonal-reproduction animals, this study aimed to investigate for the first time the potential role of melatonin on testicular blood flow (TBF) in Shiba goats. Twelve sexually mature (1.5–3 years) male Shiba goats were exposed to a single S/C injection of either melatonin in corn oil suspension (Mel group; 36 mg/goat; n=5) or corn oil only (Cont. group; n=7). Monitoring the changes in TBF was performed 1 week before, at time of injection (W0), and once a week for W8 after injection using color Doppler ultrasonography. Plasma levels of FSH, LH, testosterone (T) and estradiol (E2) were determined by RIA. Plasma levels of melatonin and nitric oxide were measured using enzyme immunoassay kits. Results revealed significant decreases in the Doppler indices (resistive index; RI, pulsatility index; PI) of the testicular artery starting from W2 till W6 in Mel group. Peak systolic velocity and end diastolic velocity of TBF showed non-significant changes among the two groups. Significant increases in FSH, LH, T, and Mel in the Mel group. E2 and nitric oxide were significantly increased coinciding with decreases in the values of Doppler indices. Three explanations may be involved. First is the direct effect of Mel on TBF due to previous evidence of expressions of Mel receptors in the testis. Second is attributable to indirect effects of Mel as a powerful biological antioxidant inside the body. The third may be due to its influence on E2 and nitric oxide that have vasodilatory effects on the testicular artery. In conclusion, Mel may have a stimulatory effect on testicular blood flow in Shiba goats and pursue improve male fertility. |
