Background & Objectives: Stress in developing countries is an important problem in human health. Feelings of stress in humans result from interactions between persons and their environment. Stressor is an external stimulus or an event that provokes a stress response in an organism. Animal models enable preclinical testing of new treatments and therapies for physical symptoms of stress disorder. In the present study the effects of social stress on male mouse reproductive system were investigated.

  Methods: Sixty male mice were divided into 6 groups, including two non-stressed control groups (2 cages, 5 mice per cage), two mild-stressed groups (2 cages, 10 mice per cage), and two high-stressed groups (2 cages, 15 mice per cage). Three cages (one cage from each group) kept for one month and three cages kept for two months. After one and two months the mice were anaesthetized with ketamine and xylazine. Tissue samples of testes , epididymis and vas deferens for light microscopy were removed . Data analysis was performed using one-way ANOVA. P<0.05 was considered significant.

  Results: The results showed that there was no significant difference between mild and high-stresses groups in the diameter of seminiferous tubules, vas deferens, height of epithelial cells of epididymis and vas deferens. The diameter of epididymis in mild and high-stressed groups was significantly decreased as compared with that in non-stressed control groups (P<0.02, P<0.009). The diameter of vas deferens in mild-stressed groups was significantly decreased as compared with in non-stressed control groups (P<0.02). The height of epithelial cells of vas deferens in mild and high-stressed groups was significantly decreased as compared with that in non-stressed control groups (P<0.001, P<0.001).

  Conclusion: This study shows that crowding stress can decrease the diameter and height of epithelial cells of epididymis and vas deferens of male mice .