Effect of a left atrium-pulmonary vein baroreflex on peripheral vascular beds.

A step increase of left atrial and pulmonary venous pressure from 0 to 25 mmHg was used in anesthetized dogs with controlled arterial blood pressure to generate reflex systemic vasodilation. The resultant response of total peripheral resistance was an initial transient fall of about 40% which spontaneously regressed while the stimulus was maintained. Injections of differently tagged radioactive microspheres were used to measure selected organ blood flows prior to raising atrial pressure, at the response peak, during the steady state, and after recovery. Resistances of skin, skeletal muscle, kidney, and large intestine significantly fell upon atriovenous distention. The response in muscle, which greatly exceeded that of the other organs, was not sustained, whereas resistances of other responding beds remained depressed until the stimulus was removed. No significant responses occurred in small intestine, liver (hepatic artery), or adrenal gland.