Spontaneous contractile characteristics, as well as inotropic influences of norepinephrine (NE) and prostaglandin E1 (PGE1) on different sow oviductal segments isolated from preovulatory or early postovulatory period, were explored. Postovulatory fimbrial preparations contracted with higher intensity and slower frequency than preovulatory ones whereas the spontaneous motility of other regions were comparable at both stages. Norepinephrine (NE) depressed preovulatory ampullar and fimbrio-ampullar portions but stimulated fimbrial and isthmic segments. However, after ovulation NE enhanced the motility of all tubal regions, particularly the fimbrial ones. Phentolamine abolished and even reversed, on postovulatory ampulla, the contractile augmentation elicited by NE. PGE1 markedly diminished the tension and frequency of preovulatory fimbrial and fimbrio-ampullar segments but it was inactive on other ampullar regions. This depressant influence on the preovulatory fimbrio-ampullar region was replaced, a few hours following ovulation, by a distinct contractile increment. Although phentolamine failed to alter the PGE1 postovulatory ampullar influences, it clearly blunted the PGE1 enhancement of postovulatory isthmic motility. The results suggest that changes observed in adrenergic or postaglandinic responses of the sow oviduct may be linked to influences exerted by rapid variations of circulating substances associated with the ovulatory process. Furthermore it is also plausible that the action of PGE1 on the isthmus but not on the ampulla is undirect and attributable, at least in part, to the release of NE. It finally appears that the fimbrio-ampullar junction of the domestic sow acts as a "prostaglandin sphincter" able to avoid the loss of oocytes newly introduced into the oviduct.