Ochillo_1982_Arch.Int.Pharmacodyn.Ther_257_104

We have investigated the effects of indomethacin, a potent prostaglandin synthesis inhibitor, and PGE2 on the acetylcholine-initiated contractions of isolated gastric muscularis muscle of Bufo marinus. Two types of contractions were identified: initial contraction observed on challenging the preparation with acetylcholine (ACh) and, spontaneous contractions which persisted after the initial contraction. The challenging dose of ACh (2.5 X 10(-5) M) was fixed at the level eliciting optimum contractions of the preparation while the dose of indomethacin was varied between 0-2.5 X 10(-4) M. Indomethacin dose of 5.0 X 10(-6) M prevented the spontaneous contractions but had no noticeable effect on the initial contraction. However, the initial contraction was inhibited by indomethacin in a dose-dependent fashion with a complete blockade occurring at an indomethacin dose of 2.5 X 10(-4) M. To rule out the possibility of indomethacin dose being non-specific in this preparation, PGE2 (10(-7) M) was used to reverse the reduction of the spontaneous contractions elicited by indomethacin (4.0 X 10(-5) M) and the antagonism was surmountable. We concluded that PGE2, and/or other related endogenous compounds play a part in cholinergic-initiated contractions of muscularis muscle of Bufo marinus.