THE EFFECT OF N-METHYL-N-CINNAMYL-2-PHENYL-PROPYLAMINE (MRD-255) ON CORONARY CIRCULATION, CARDIAC WORK AND MYOCARDIAL OXYGEN UTILIZATION IN THE DOG

¹ Department of Pharmacology, University of Illinois College of Medicine, Chicago

The effects of N-methyl-N-cinnamyl-2-phenylpropylamine (MRD-255) and papaverine on coronary blood flow were studied in the open-chest anesthetized dog, utilizing both the technique of coronary sinus outflow and coronary artery inflow. Cardiac work and cardiac oxygen utilization were determined.

Intravenous and intraarterial administration of MRD-255 resulted in an increase in coronary blood flow of equal magnitude but longer duration than that produced by equal doses of papaverine. In addition, there was no fall in blood pressure with intravenous administration of MRD-255, as contrasted with the marked hypotensive response to papaverine at doses above 1 mg/kg body weight.

Both MRD-255 and papaverine resulted in an increased coronary blood flow in the absence of significant changes in either cardiac work or cardiac oxygen utilization. The oxygen concentration of the coronary venous blood was greatly increased during the period of the increased coronary blood flow, indicating an oxygen supply far in excess of the metabolic demands of the myocardium.