Temporal relationship between changes in oxytocin and prostaglandin F levels in response to vaginal distension in the pregnant and puerperal ewe.

To investigate the rôle of oxytocin in the increase in utero-ovarian venous prostaglandin F (PGF) level caused by vaginal distension, jugular venous oxytocin and utero-ovarian venous PGF were measured simultaneously in one sheep in late pregnancy and in one sheep shortly before parturition. Vaginal distension raised oxytocin and PGF levels in both animals and oxytocin levels increased before those of PGF. These findings support the suggestion that the elevated PGF levels resulting from vaginal distension are caused by the reflex secretion of oxytocin.