Responsiveness of rat vas deferens and stomach smooth muscles after treatment with indomethacin

The contractile responses of rat vas deferens and longitudinal stomach fundus strips to stimulants and relaxants were studied after treatment with indomethacin (Ind) injected i.p. at doses of 15 mg/kg for 24 hr and 25 mg/kg for 48 hr. The treatment with Ind reduced the amount of both spontaneously and electrically-evoked release of a prostaglandin (PG)-like substance from the isolated n. hypogastricus-vas deferens preparations. A considerable decrease of the responsiveness to exogeneous noradrenaline occurred in vas deferens isolated from Ind-pretreated rats. The EC50 values of noradrenaline increased as compared to the control value. The contractile responses of the isolated longitudinal stomach fundus strips to acetylcholine, serotonin, PGE2, PGF2 and arachidonic acid were reduced while the relaxant action of noradrenaline and papaverine was potentiated after Ind treatment. It is assumed that endogeneous PGs participate in the regulation of smooth muscle activity through potentiation of the postjunctional excitatory action of noradrenaline in vas deferens and through interaction with the transmembrane ion transport in stomach fundus smooth muscles.