Neurogenic control of skeletal muscle vascular resistance in hemorrhagic shock

¹ Department of Physiology, Indiana University School of Medicine, Indianapolis, Indiana

The neural control of the resistance vessels of a gracilis muscle, isolated except for its nerve, was monitored during the various phases of hemorrhagic shock in dogs. The circulation to the muscle was maintained at a constant pressure of 160 mm Hg with a pump, using blood from a donor dog to eliminate any blood-borne factors elaborated by the shock dog. The degree of neural vasoconstriction was evaluated by periodically blocking the nerve with cold and measuring the subsequent changes in blood flow. Vasoconstriction followed hemorrhage. In many of the experiments there was evidence of loss of neural control of vascular resistance after prolonged hypotension following hemorrhage or terminally following the progressive decline in blood pressure after transfusion. This reduction of neurogenic vasoconstriction may contribute to cardiovascular collapse during hypotension. Following transfusion, however, vasoconstriction greater than control was generally seen, suggesting a functioning homeostatic mechanism acting to maintain the declining arterial blood pressure. Thus, irreversibility following transfusion is not the result of a loss of neurogenic control of the vascular resistance of skeletal muscle under the conditions used.

Note:
With the Technical Assistance of J. Ralph Love and Richard Jacks