Multiple sclerosis (MS) is one of the degenerative diseases of the central nervous system (CNS), which results in the destruction of myelin sheath. MS could be induced in laboratory animals, by injection of ethidium bromide (EB) into Cerebrospinal Fluid (CSF). This disease may cause impotence or subfertility in men. The objective of this study was to evaluate the role of MS on spermatogenesis, sperm parameters such as… and sex hormones of wistar rats. A total of 36 rats (5 weeks old) were divided into 3 groups of control, sham and experimental. 20ul of physiological saline was injected into cerebellomedullary cistern (CC) of rats in sham group, and, 20ul of EB was injected into CC of experimental group. One week after EB injection, two rats from each group were killed randomly to investigate the morphology of pons. The rest were killed 5 weeks after injections to study the spermatogenic cells, sperm parameters and sex hormones. The results showed that sperm progressive motility was significantly reduced from 74.4 2.2 in control group to 60.61.4 in experimental group (p<0/001). Also, the number of round cells was increased from /73 0/1 in control group to 2.16 /25 in experimental group (p

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