Coronary Artery Vasodilation in the Canine

Abstract

The role of beta 1- and beta 2-receptors as modulators of coronary artery vasodilation was studied in the anesthetized dog. The left circumflex coronary artery was cannulated and perfused under constant pressure with blood drawn from the right femoral artery. Coronary blood flow myocardial contractile force were measured with a cannulating electromagnetic flow probe and Walton-Brodie strain gauges, respectively. The left stellate ganglion was isolated distally, and the postganglionic nerves were stimulated with a bipolar electrode. Coronary artery blood flow and regional myocardial contractile force increased in response to stellate nerve stimulation and to the intracoronary administration of norepinephrine (NE), isoproterenol (ISO), and zinterol (ZIN) before selective beta 1-adrenergic receptor blockade with celiprolol (0.3 mg/kg intravenously, i.v.). The administration of celiprolol inhibited the positive inotropic response to both stellate stimulation and to the intracoronary administration of the selected beta-adrenergic receptor agonists. The increase in coronary artery blood flow observed in response to stellate stimulation or to the intracoronary administration of NE was converted to a decrease in flow in the presence of celiprolol. In contrast, however, the intracoronary administration of ISO or ZIN continued to cause coronary vasodilation despite the presence of beta 1-selective adrenergic receptor blockade with celiprolol. Addition of propranolol (1.0 mg/kg i.v.) in the presence of celiprolol completely inhibited the increase in coronary blood flow in response to ISO and ZIN.(ABSTRACT TRUNCATED AT 250 WORDS)