Relaxing action of Trepibutone (AA-149) on the isolated sphincter of oddi and small intestine of rabbits.

We investigated the smooth muscle relaxing action of trepibutone [3-(2, 4, 5-triethoxybenzoyl)pro pi onic acid: AA-149] using assays of the isolated preparations of sphincter of Oddi, duodenum, jejunum and ileum of rabbits. Trepibutone (10-6-10-3 M) markedly relaxed the sphincter of Oddi and duodenum, while papaverine (10-6-10-4M) exerted an equipotent relaxing activity in all these preparations. The actions of trepibutone were not altered by pretreatment with tetrodotoxin, phentolamine or propranolol. However, trepibutone at a concentration of 3×10-3 M, unlike papaverine, had no effect on the contractile response to ACh. These results indicate that trepibutone relaxes smooth muscle by a direct action which differs from the action of papaverine.