Influences of selective sympathetic denervation on coronary reactive hyperemia in conscious dogs.
Mongrel dogs were chronically instrumented to measure left circumflex coronary flow, arterial pressure, left atrial pressure, ECG, heart rate and in some cases, left ventricular pressure or cardiac output. A cuff type occluder was placed distal to the flow probe. Total occlusion of the left circumflex coronary artery for one minute in unsedated, resting dogs produced reactive hyperemia with an average replacement/deficit ratio of 2.63/1. In 11 dogs, sympathetic influences were investigated by chronic surgical cardiac sympathectomy. Surgical section of all ansae subclaviae responses from 2.61/1 to 1.67/1 (P less than 0.001). Left sympathectomy alone had no effect on the replacement/deficit ratio whereas selective right sympathectomy reduced it from 2.25/1 to 1.38/1. Pharmacological blockade was used to determine beta-receptor involvement in the responses. In 9 intact dogs practolol (10 mg/kg) reduced the reactive hyperemia ratio by 12% (P less than 0.05). Propranolol (1 mg/kg) further reduced this ratio by 30% (P less than 0.001). Our results suggest that sympathetic beta influences work primarily through the right cardiac sympathetic nerves. Also, the magnitude of the response appears to be due, in part, to increased metabolic activity associated with myocardial beta 1-receptors and heart rate increase as well as active vasodilation through beta 2-receptors.
D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000294:innervation*; D003714:Denervation; D004285:Dogs; D004525:Efferent Pathways / Q000502:physiology; D006439:Hemodynamics / Q000187:drug effects; D011217:Practolol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012018:Reflex / Q000502:physiology
D011433:Propranolol; D011217:Practolol