Antagonistic activity of verapamil and diltiazem against different intestinal smooth muscle stimuli

Investigations in the isolated guinea-pig ileum have shown an almost equal inhibitory activity of verapamil and diltiazem against contractions elicited by histamine, 5-HT, acetylcholine and BaCl2. While dicycloverine (dicyclomine) has a specific anticholinergic action, no specific action against any of the stimulating compounds including BaCl2 could be differentiated. Verapamil and diltiazem seem to have good oral "unspecific" spasmolytic properties, which might be of clinical value. The results let us assume that the site of the calcium antagonists action of verapamil and diltiazem in the intestinal smooth muscle could be at a common entrance of Ca2+ released by receptor operating compounds and of Ba2+ into the cell or at structures from which BaCl2 as well as the other agonists release Ca2+.