Vasomotor responses in a resting musculocutaneous area during muscular activity

¹ Laboratory of Cardiovascular Physiology, National Heart Institute, National Institutes of Health, Bethesda, Maryland

The vasomotor responses in a resting musculocutaneous area, when muscular contractions were electrically induced in another area, were studied in anesthetized dog preparations. The responses consist of an initial transient vasodilatation of substantial magnitude followed by a modest vasoconstriction. The initial vasodilatation was not modified by atropine sulfate but was absent during ganglionic blockade with tetraethylammonium chloride and after surgical sympathectomy. This suggests that the initial vasodilatation is due to a brief diminution in sympathetic vasoconstrictor activity and not to activation of cholinergic sympathetic vasodilator fibers. It is thought likely that the transient diminution in sympathetic vasoconstrictor activity observed in a resting muscular area also occurs simultaneously in the exercising muscular area and thus plays a role in augmenting blood flow to active muscular areas in the initial moments of the transition from rest to exercise.