Tsai_1987_Res.Commun.Chem.Pathol.Pharmacol_58_273

We have investigated the effects of phenylbutazone (PBZ), a potent prostaglandin (PG) synthesis inhibitor, on the acetylcholine (ACh)-initiated contractions of isolated gastric muscularis muscle of Bufo marinus. Two types of contractions were identified: tonic contractions and spontaneous contractions. The challenging dose of ACh (1.0 X 10(-4)M) was fixed at the level eliciting optimum contractions of the preparation while the dose of PBZ was varied between 0-5.0 X 10(-4)M. PBZ dose of 1.0 X 10(-4)M suppressed the spontaneous contractions but had no noticeable effect on the tonic contractions. To further elucidate the mechanism through which PBZ suppressed the spontaneous contractions, prostaglandin E2 (PGE2) (10(-7)M) was used to reverse the suppression induced by PBZ (5.0 X 10(-5)M). We concluded that PGE2 plays a part in the manifestation of the cholinergic-initiated contractions of the muscularis muscle of Bufo marinus and the effects of PBZ can be surmounted by administration of PGE2 exogenously.