Myogenic hyperemia following brief tetanus of canine skeletal muscle.

MOHRMAN, DAVID E., AND HARVEY V. SPARKS. Myogenic hyperemia following brief tetanus of canine skeletal muscle. Am. J. Physiol. 227(3) : 531-535. We have tested the hypothesis that a portion of the vasodilatory response to brief (1 s) tetanus could be initiated by the rapid alterations in extravascular pressure and in vascular transmural pressure associated with muscle contraction. Dogs were anesthetized with pentobarbital and the calf muscles were isolated so that vascular responses could be studied under conditions of constant flow or constant pressure. An inflatable cuff was placed around the calf to provide a means of increasing extravascular pressure in the absence of muscle contraction. Intramuscular pressure was estimated with a small, fluid-filled balloon placed deep within the muscles and connected to a low-displacement pressure transducer. Intramuscular balloon pressure increased linearly with increased gastrocnemius tension development caused by increased stimulation frequency (16-64 impulses/s). Elevation of intramuscular balloon pressure to the same level caused by tetanic stimulation resulted in a vasodilatory response which was approximately one-half as large as that following tetanic contraction when flow was constant and approximately one-third as large when pressure was constant. We conclude that a portion, but not all, of the vasodilation following brief tetanus of skeletal muscle may be a response to alterations in vascular transmural pressure associated with tetanic contraction.