AbstractBisnordihydrotoxiferine and vellosimine, two tertiary indole alkaloids have been isolated from the root ofStrychnos divaricans. Bisnordihydrotoxiferine antagonized in a nonspecific manner, oxytocin and acetylcholine induced contractions in the rat uterus and acetylcholine and histamine responses in the guinea‐pig ileum. Bisnordihydrotoxiferine, like verapamil, produced effects on voltage dependent Ca2+channels. For example in guinea‐pig ileum, bisnordihydrotoxiferine (pD'23.92±0.09) and verapamil (pD'26.00±0.11) inhibited KCl induced contractions. Furthermore, bisnordihydrotoxiferine (pD'24.37±0.02) and verapamil (pD'26.83±0.10) also antagonized CaCl2induced contractions of K+‐depolarized rat uterus. When compared with sodium nitroprusside, an antagonist of receptor operated Ca2+channels, bisnordihydrotoxiferine had no effect. However, in the aorta, the alkaloid (IC50, 6.10 × 10−6M) antagonized the intracellular calcium dependent transient contractions of noradrenaline and it was about four times more potent than procaine (IC50, 2.30 × 10−5M), a known inhibitor of the release of Ca2+from intracellular stores. Bisnordihydrotoxiferine may produce nonspecific spasmolytic actions mainly by inhibiting intracellular calcium mobilization and to a lesser extent by inhibiting voltage dependent calcium channels in