EFFECTS OF OXYTOCIN ON SPERM TRANSPORT IN THE PUBERTAL RAT

Oxytocin is present in the mammalian testis where it increases contrac tility of seminiferous tubules in vitro and has been implicated in spe rm transport. The present study investigated whether oxytocin affects the transport of spermatozoa from the testis in vivo. In rats, mature spermatozoa are first seen in the testis 42 days postpartum and arrive in the epididymis at about day 45. Male Wistar rats were given daily subcutaneous injections of either oxytocin (0.5 mu g), the oxytocin an tagonist des Gly-NH(2)d(CH2)(5)-[D-Tyr(2),Thr(4)]OVT (0.2 mu g) or sal ine from day 40 postpartum. Groups of six animals were killed 2 h afte r their last injection on days 43, 44, 45 and 46 postpartum. Testes we re removed and fixed in Bouin's fluid for histological examination and the number of spermatozoa in the epididymides was counted. Spermatozo a were seen in the epididymis earlier in the oxytocin-treated rats (da y 43) than in the control animals (day 44), and treatment with the ant agonist delayed the appearance of spermatozoa in the-epididymis until day 45. When the testes were examined, residual bodies, which were use d as an indicator of spermiation, were seen only in one control animal before day 44. Residual bodies were seen in the testes of all oxytoci n-treated rats on day 43 but were not detected until day 45 in the oxy tocin antagonist-treated rats. These data show that in rats oxytocin c an affect the arrival of spermatozoa in the epididymis. Although this may be due in part to effects on tubal transport or the secretion of t ubular fluid, these findings suggest that the peptide may affect sperm iation.