Cardiovascular actions of DPI 201-106, a novel cardiotonic agent

DPI 201-106 (4-[3-(4-diphenylmethyl-1-piperazinyl)-2-hydroxypropoxy]-1H-indole -2- carbonitrile) is characterized by a marked cardiotonic activity. The compound exerted positive inotropic effects in anesthetized and conscious dogs, pithed open-chest cats, and isolated hearts of cardiomyopathic hamsters and vanadate-treated guinea-pig atria. Left ventricular dP/dtmax was increased in anesthetized dogs after i.v. injection of 0.2 and 2 mg/kg DPI 201-106 (34 +/- 6 and 104 +/- 18%, respectively) and in unanesthetized dogs after oral doses of 2-8 mg/kg (22 +/- 3 to 50 +/- 5%, respectively). In most experiments, the compound lowered blood pressure and heart rate. Stroke work and left ventricular work were almost unaffected by DPI 201-106, and oxygen consumption and cardiac efficiency remained unchanged in open-chest dogs. Studies of the mechanism of action of DPI 201-106 lead to the conclusion that its positive inotropic effect is not explainable either by beta-stimulation or by liberation of catecholamines. This was shown in anesthetized dogs and pithed open-chest cats pretreated with propranolol and reserpine.