Abstract
The antagonistic effects of two new β-receptors blocking agents, Kö 1313 and Kö 1366 against the chronotropic and inotropic responses to noradrenaline and tyramine were studied on the isolated right and left atria of guinea-pigs. From the KB values estimated by means of three different methods, it was found that the potencies of Kö 1366 were 5 to 10 times and 5 to 7 times those of Kö 1313 in the antagonism against chronotropic and inotropic effects of noradrenaline respectively. From the depression of maximum chronotropic and inotropic effects of tyramine in the presence of these agents, Kö 1366 was demonstrated to be approx. three times more potent than Kö 1313 in the antagonism against both effects of tyramine.
