Neural and Metabolic Control of Blood Flow to Respiratory Muscles of Rabbits

Abstract

Regional blood flow was measured in respiratory muscles, limb muscles, and kidneys of rabbits anesthetized with sodium pentobarbital. Flow measurements were made by the use of radioactive microspheres. The responses to graded aortic nerve (AN) stimulation on regional blood flows at different levels of inspiratory resistance were determined. As the inspiratory load was increased blood flow to respiratory muscles increased due to a decreased vascular resistance. Blood flow to the limb muscle and kidneys decreased. Stimulation of the AN increased blood flow and decreased vascular resistance in the respiratory muscles at all levels of respiratory activity studied. The stimulus-response curves to AN stimulation were similar in paralyzed animals, animals breathing quietly, and in animals breathing against an inspiratory resistance sufficient to produce a peak inspiratory pressure of 15 mm Hg. These results suggest that sympathetic control of the blood flow to respiratory muscles may be important during normal breathing and during labored breathing where metabolic vasodilation exists.