CORONARY PRESSURE-BLOOD FLOW RELATIONS - EFFECT OF NOREPINEPHRINE

Coronary pressure-blood flow relations were studied in anesthetized dogs by changing blood flow in the left main coronary artery and measuring coronary pressure before, during and after intracoronary norepinephrine infusion. Norepinephrine produced an increase in coronary vascular resistance in 10 of 28 experiments, usually in experimental preparations with a low initial coronary resistance. This increase in resistance occurred at different blood flow rates and was therefore not dependent on the rate of blood flow. Prior to norepinephrine infusion, coronary pressure-blood flow curves were curvilinear, convex to the pressure axis, showing a decrease in resistance with increasing blood flow except in those preparations with a low resistance in the control period. In these, resistance did not fall as flow increased from the low to the mid-flow range, but did fall as blood flow increased further. © 1969.