Influence of prostaglandins on the spontaneous motility of pig oviducts

The effects of prostaglandins (PG) F_2α and E₂ on the spontaneous motility of pig oviducts were studied in vivo and in vitro using intraluminal pressure transducers. PGF_2α always increased the muscular activity of the oviducts, gradually augmenting their sensitivity to PGF_2α stimulation from pro-oestrus, reaching their highest responsiveness at the peri-ovulatory stage, and decreasing thereafter. PGE₂ elicited inhibitory responses from the tubal preparations during oestrus and the third day of the cycle in vivo, and during pro-oestrus and oestrus in vitro. The isthmic longitudinal muscle layer was always contracted by the exogenous PGE₂ in vitro. During the luteal phase, PGE₂ elicited a stimulatory response both in vivo and in vitro, of a similar type of that of the PGF_2α. These stimulatory responses could be blunted, but not abolished, by selective blocking of α-adrenoceptors in vitro. Indomethacin inhibited in a concentration-dependent manner the spontaneous motility of the pig oviducts in vitro. This inhibition was reversible and the spontaneous motility could be fully restored after total abolition of activity by addition of PGF_2α, but not of noradrenaline, which only increased the tonus of the inhibited preparations.