More evidence of how essential oxytocin is to males, not only for their general health but also for their sexual functioning, comes from this article in Human Reproduction Update.
Researchers Hemlata Thackare, Helen Nicholson and Kate Whittington write,
At ejaculation, a burst of OT [oxytocin] is released from the neurohypophysis into the systemic circulation and stimulates contractions of the reproductive tract aiding sperm release.
So, men experience the same oxytocin pulse at orgasm that women do.
The researchers add that there's conclusive evidence that oxytocin is synthesized in the testes of mammals, and it plays a role in stimulating contractions of the seminiferous tubules (where sperm is produced), the epididymis (where sperm matures) and the prostate gland.
Because oxytocin affects the growth of the prostate directly and also by moderating the effects of androgens, they speculate that it may lead to new treatments for prostrate cancer.