[Action mechanism of vascular spasmolytics. 5. Drug-related relaxation and adenosine-3',5'-monophosphate content of isolated coronary arteries under conditions of fluoride-induced contracture].

Tetracaine and SKF 525-A as well as stimulators of adenylate cyclase and inhibitors of the nucleoside-3',5'-monophosphate phosphodiesterase have spasmolytic effects. At the fluoride-iuduced contracture -- a form of contracture independent of extracellular calcium -- tetracaine and SKF 525-A effect an additional increase in muscular tension. Their relaxing effect evidently presupposes a functioning calcium exchange. Drugs acting on the cAMP system have invariably spasmolytic effects at this contracture model, although they produced no change of the cAMP content under these conditions. An increase in total cAMP content is not obviously a necessary condition for the occurrence of drug-induced relaxation.