The Influence of Sympathetic Adrenergic Vasoconstrictor Nerves on Transport of Diffusible Solutes from Blood to Tissues in Skeletal Muscle

Arteriovenous (A‐V) extraction of rubidium ‐86 was continuously recorded in isolated skeletal muscles of dogs and cats perfused with blood at constant flow. In a few experiments, A‐V extraction of oxygen was measured also. The sympathetic trunk, still connected to the muscle, was stimulated electrically under various conditions. Excitation of sympathetic adrenergic vasoconstrictor nerves produced an increase in vascular resistance and a decrease in Rb86 and O2 transport. These effects were graded in relation to stimulus frequency, persistent throughout continued stimulation and large enough to be of importance at low, physiological frequencies. The changes in vascular resistance and blood‐tissue transport are mechanically independent. Both are mediated by preganglionic fibers of similar properties, but it is not possible to tell if the same or different fibers are involved. The reduction in transport is considered to result mainly from restriction of the number of open capillaries, due to closure of precapillary sphincters, with some contribution from a decrease in the uniformity of circulation through those parts of the capillary network remaining open