AJP - Heart and Circulatory Physiology, Vol 249, Issue 2 337-H343, Copyright © 1985 by American Physiological Society
Parasympathetic control of transmural coronary blood flow in dogs
J. V. Reid, B. R. Ito, A. H. Huang, C. W. Buffington and E. O. Feigl
The transmural distribution of coronary blood flow was studied during vagal
stimulation in closed-chest, morphine- and alpha-chloralose-anesthetized
dogs. The left main coronary artery was cannulated and perfused at constant
pressure. Bradycardia during vagal stimulation was prevented by
atrioventricular heart block and ventricular pacing. Beta-adrenergic
receptors were blocked with propranolol (1 mg/kg iv), and aortic pressure
was stabilized by means of a pressure reservoir. Regional myocardial blood
flow was measured with 9-micron radioactive microspheres during vagal
stimulation and during intracoronary acetylcholine infusion. Vagal
stimulation increased coronary blood flow uniformly across the left
ventricular wall. In contrast, intracoronary acetylcholine infusion, at a
rate selected to increase total flow to the same degree, vasodilated the
subendocardium more than the subepicardium, increasing the inner/outer
blood flow ratio. It is concluded that both vagal activation and
acetylcholine produce coronary vasodilation that is independent of left
ventricular preload, afterload, and heart rate. Acetylcholine vasodilation
preferentially vasodilates the subendocardium, increasing the inner/outer
flow ratio, but vagal stimulation produces uniform vasodilation across the
left ventricular wall.
