A study of compounds which inhibit vascular smooth muscle contraction

Abstract

Several compounds have been examined for their inhibitory action on a rat aortic ring preparation stimulated by four different agonists, noradrenaline bitartrate (NA), Ba 2+, Ca 2+ and K +. The compounds tested include phentolamine, papaverine, cinnarizine, cyclandelate, SKF-525A, prenylamine, guancydine, verapamil and compound D-600. Phentolamine inhibited NA reponses at much lower concentrations than those required to antagonize K +, Ca 2+ or Ba 2+ responses. Guancydine was also more effective against NA but was much less potent than phentolamine in this respect. Papaverine, cinnarizine, cyclandelate, prenylamine and SKF-525A were non selective agents and inhibited responses to all agonists approximately equally at various concentrations. Verapamil and D-600 were highly potent compounds which were more effective against cation-induced responses, especially those to Ca 2+, than against those induced by NA.