Abstract

Introduction: Several clinical studies indicate deterioration of sexual behavior in diabetic patients. The pathophysiological mechanisms of diabetic sexual impotence remain obscure. In this study the therapeutic effects of melatonin on sexual behavior were investigated through the central serotonergic system in diabetic rats. Materials and Methods: In this study, 30 male adult Wistar rats, weighing 200±20 g, were used. Animals were divided into three groups, the controls (C), diabetic (D) and the melatonin-treated diabetic (M) group. Experimental diabetes was induced by intraperitoneal injection of 50 mg/kg streptozotocin. Melatonin was injected (10 mg/kg i. p. ) after 3 days of streptozotocin injection for 30 days. At the end of the administration period, the sexual behavior of each male rat to an ovariectomized female rat was assessed for 40 min. Serotonergic type 2 (5-HT_2A) receptor activities were investigated through spontaneous WDS behavior, and experimental data were statistically analyzed. Results: First mount, first intromission and first ejaculation latencies significantly (p<0. 05) increased in diabetic rats as compared to controls. Melatonin treatment significantly (p<0. 05) reduced these responses in the M group, compared to the D one. Also the number of mounts, intromissions and ejaculations significantly (p<0. 05) decreased in diabetic rats compared to controls. Administration of melatonin significantly (p<0. 05) increased these activities in the M group as compared to the D one. Calculation of copulatory efficiency and the sexual activity index of each rat indicate that reproductive activity in diabetic rats was significantly (p<0. 05) less than other two groups. The number of WDS responses was significantly (p<0. 05) different in all three groups. Conclusion: Sexual dysfunction in diabetic animals was accompanied by decreasing of 5-HT_2A receptor activities, and melatonin prevented the diabetes-induced sexual impotence by modulating of central serotonergic system activity.