Effect of Sympathetic Nerve Stimulation on Cutaneous Small Vein and Small Artery Pressures, Blood Flow and Hindpaw Volume in the Dog

Abstract

Electrical stimulation of the lumbar sympathetic chain in dogs produced a variety of response patterns in pressures measured in the femoral artery, a small cutaneous artery (saphenous) and a small cutaneous vein. The preponderant response in the small vein during stimulation was a rise from an average control value of 17 mm Hg to an average value of 30 mm Hg. Shortly after cessation of stimulation a secondary pressure rise occurred to an average value of 42 mm Hg. The average small artery pressure changed from 99 mm Hg to 138 mm Hg during stimulation and fell to 55 mm Hg shortly after stimulation ended. Both pressures then gradually returned to control levels. Hindpaw volume and saphenous artery blood flow invariably showed an abrupt decrease during sympathetic nerve stimulation. An increase in small vein pressure associated with decreased blood flow is interpreted to be due to an increase in resistance to run off from the venous bed. Marked increases in small vein pressure occurred following sympathetic stimulation for as long as ten minutes after cessation of respiration and cardiac contraction. Control experiments excluded changes in cardiac output, central venous pressure and skeletal muscle movement as significant factors in the observed changes. Therefore the small veins as well as the small arteries of the skin of the hindpaw in the dog are capable of constricting in response to sympathetic nerve stimulation to produce marked increases in intraluminal pressure. The small vein can react independently of the small artery.