Introduction & Objective: Melatonin, the most important secretary hormone of pineal gland, as a powerful antioxidant has a high potent for neutralizing the toxicity of drugs. In the present study we aimed to demonstrate the effect of melatonin on testicular damage and sperm parameters deficiency induced by acetylsalicylic acid, in adult male mice.

Materials & Methods: Male NMRI mice were divided into 4 groups: 1) control 2) acetylsalicylic acid treated group 3) melatonin treated group 4) Melatonin-acetylsalicylic acid treated group. Acetylsalicylic acid was administered at a dose of 50mg/kg orally through gavage for 14 days. Melatonin was administered in dose of 10 mg/kg for 5 days intraperitoneally. The control mice were received vehicle (normal saline) orally through gavage. The animals were sacrificed and their testes and epididymis were dissected on the 15th day after the treatment. Evaluations were made by determining Johnson's score, epididymal sperm count, and sperm morphology and sperm motility. Statistical analysis was performed by ANOVA test.

Results: Acetylsalicylic acid treated mice showed a reduction in Johnson's score and quality of spermatogenesis (P<0.05), sperm count, normal morphology and motility percent (P<0.001), compared to the control. Melatonin in group 4, significantly increased maturation of seminiferous tubules (P<0.05), and quality and quantity of sperm parameters (P<0.05) in comparison with group 2.

Conclusion: It seems that intraperitoneal administration of melatonin for 5 days is a potentially beneficial agent to improve the quality of spermatogenesis and sperm parameters in testis damaged by acetylsalicylic acid, probably by decreasing oxidative stresses.