Trinervine, a new tertiary indole alkaloid of sarpagine like skeleton with a hemiketal function, isolated from the root bark of Strychnos trinervis was submitted to a broad spectrum pharmacological screening, when the principal effect observed was a nonspecific relaxation of isolated smooth muscles. The spasmolytic actions were confirmed on cumulative concentration-response curves using carbachol and histamine induced contractions of the guinea-pig ileum and 5-hydroxytryptamine (5-HT) and arachidonic acid contractions in the rat fundic strip. The respective pD'2 values (mean ± SE) were 4.04 ± 0.12 and 4.25 ± 0.16, in the guinea-pig ileum and 3.54 ± 0.15 and 3.96 ± 0.16 in the rat fundic strips but trinervine was found inactive against PGE2 induced contractions at concentrations up to 10(-4)M. The values of slopes of the regression lines differed significantly from the unity in all cases and as the maximum effect of the agonists were suppressed, these preliminary results suggest that trinervine produce spasmolytic effects on isolated gastrointestinal smooth muscles through noncompetitive antagonism process.