[Experimental studies on the mechanism of action of carbocromen on the isolated cat papillary muscle (author's transl)].

1. In isotonically shortening cat papillary muscle 3-(2-di-ethylaminoethyl)-4-methyl-7-(carbethoxy-methoxy)-2-oxo-1,2-chromene-hydrochloride (carbocromen; Intensain¿) (1-30 mug/ml) slightly increases contraction amplitude. 2. At low stimulation rates (6-12/min) the positive inotropic effect is more pronounced. 3. The maximal velocity of depolarization of the monophasic action potential is slightly reduced. 4. At all stimulation frequencies investigated (15-90/min) the total duration of the action potential -- especially at late repolarization level -- is strongly increased. Hence, functional refractory period is prolonged and maximal follow frequency reduced.