Endocrine Abstracts

Oxytocin was suggested to affect sperm volume and ejaculation. The most distal part of the epididymis stores the sperm until ejaculation and was therefore our main focus when investigating parts of the rat epididymis and vas deferens for local differences of the contractile responses to oxytocin in comparison to norepinephrine regarding their usability for targeted drug development. Single loops of the coiled epididymal duct from defined parts of the epididymis and the adjacent part of the vas deferens (DDpe) were observed using time lapse imaging and organ bath studies (n≥6). Special interest was paid to the last segment of the epididymis (S19) and the DDpe which is where the sperm is stored before release during ejaculation. The effects in the rat adult tissue with sperm were compared to the effects in neonatal tissue without any sperm present. S19 and DDpe showed a significant response to oxytocin (0,5 µM) with the response to oxytocin being significantly greater than the one to norepinephrine (10 µM). However, oxytocin showed no significant effects throughout all the other (more proximal) parts of the epididymis, responsible for sperm maturation and transport. Interestingly the same experiments conducted in the neonatal tissue again showed no significant response to oxytocin throughout all the other parts of the epididymis and a significant response in S19 and DDpe but the response to norepinephrine was always greater than oxytocin. These insights in combination with other local and central effects of oxytocin agonists and antagonists found may result in new treatment options for a variety of ejaculation associated disorders (premature ejaculation, delayed ejaculation) or as a male contraceptive.