Oxytocin‐induced contractions within rat and rabbit ejaculatory tissues are mediated by vasopressin V_1A receptors and not oxytocin receptors

Abstract

Background and purpose: Oxytocin is believed to be involved in ejaculation by increasing sperm number and contracting ejaculatory tissues. However, oxytocin may mediate these effects via oxytocin or vasopressin (AVP) receptors. The aim of this study was to determine the effect of oxytocin and AVP on peripheral tissues involved in ejaculation and to identify the receptor subtype(s) involved. Experimental approach: Standard tissue bath techniques were used to measure isometric tension from tissues involved in ejaculation and erection. Key results: Oxytocin and AVP failed to elicit a tonic contractile response in rat and rabbit testes, vas deferens, epididymis, seminal vesicles and prostate. In contrast, oxytocin and AVP elicited large tonic contractions in erectile (corpus spongiosum and corpus cavernosum) and ejaculatory (prostatic urethra, bladder neck and ejaculatory duct) tissues in a concentrationdependent manner. Conclusions and implications:The contractile effect of oxytocin on rat and rabbit ejaculatory and erectile tissues is mediated via V 1A receptors. Endothelin-1-induced contractions are not due to endogenous oxytocin or AVP release. V 1A receptor antagonists may have a therapeutic role in both erectile dysfunction and premature ejaculation.

Chronic exposure to anabolic steroids induces the muscle expression of oxytocin and a more than fiftyfold increase in circulating oxytocin in cattle

“…The most dramatic finding in sex steroid-treated muscle was the enormous increase in expression of the nonapeptide (9 amino acids) hormone OXT. This was an unexpected result as neurohypophyseal hormone OXT has previous associated functions related to muscle contraction (55,17,53) and behavior (2,39). OXT is closely related to vasopressin, differing by only two amino acids.…”

Pharmacology for the Treatment of Premature Ejaculation

“…However, the causative link between OT plasma levels and ejaculation could not be established with OT release in systemic circulation, which may be a consequence of ejaculation. Moreover, recent experiments in rats do not support a major role for peripheral OT receptors in occurrence of ejaculation (Clément et al, 2008) and rabbit, where the OT effect seems to be mediated by vasopressin 1A receptors (Gupta et al, 2008).…”

Oxytocin: recent developments

“…In animals, oxytocin can increase semen volume and number of ejaculated sperm in rams (124), induce shedding of spermatozoa from the seminiferous tubules and induce sperm movement through the reproductive tract of rats, mice and rabbits (68,69,125). Furthermore, the peak of oxytocin at orgasm is highly suggestive that oxytocin contributes to ejaculation in humans (38,72).…”