INOTROPIC AND CHRONOTROPIC EFFECTS OF VASODILATORS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 221  (3) , 609-613
Abstract
The chronotropic and inotropic effects of vasodilatos on isolated guinea pig atria (n = 163) were determined. The spontaneous frequency and the peak rate of isometric force development at a fixed frequency of 200/min were used as indexes of chronotropy and inotropy. The potency series for negative chronotropy was diltiazem > D600 [methoxyverpamil] > verapamil > lidoflaxine > bepridil > prenylamine > perhexiline > nifedipine. The potency series for negative inotropy differed substantially, exhibiting the sequence nifedipine > D600 > verapamil > bepridil > lidoflazine > prenylamine > perhexilin > dilitiazem. Nifedipine acted as an inoselective and diltiazem as a chrono-selective depressant. Other vasodilators, including papaverine, nitroglycerin, nitroprusside, adenosine, dipyridamole, diazoxide and hydralazine exerted no or negligible negative chronotropic or inotropic effects at high concentration (10-5 M). Only vasodilators classified among the Ca antagonists had appreciable direct myocardial effects. Evidently, these drugs constitute a category of agents distinct from classifical vasodilators.