Small blood vessel responses to sympathetic stimulation

¹ Department of Physiology, Medical College of Georgia, Augusta, Georgia

Three segments, an arterial, a small blood vessel, and a venous segment of the vasculature of the dog paw were isolated and studied separately to determine the temporal characteristics and the magnitude of response of each segment to a standard sympathetic stimulation. The small vessel segment responded the most rapidly, and the venous segment the least rapidly to the stimulation. The small vessel segment exhibited the most rapid recovery. Complete recovery of the arterial and venous segments required 3–5 min. A control rate of blood flow was reestablished through the arterial segment within 30–60 sec, and through the venous segment in 3–5 min, after cessation of stimulation. In some experiments blood flow was stopped completely by the sympathetic stimulation, and in all experiments the digital artery pressure was markedly decreased by the stimulation. The arteries were more effective than the arterioles in curtailing flow during the stimulation period. However, the veins were the most effective during the recovery period.