Muscle chemoreflex alters vascular conductance in nonischemic exercising skeletal muscle

Previous studies have shown that the muscle chemoreflex causes an augmented blood pressure response to exercise and partially restores blood flow to ischemic muscle. The purpose of this study was to investigate the effects of the muscle chemoreflex on blood flow to nonischemic exercising skeletal muscle. During each experiment, dogs ran at 10 kph for 8-16 min and the muscle chemoreflex was evoked by reducing hindlimb blood flow at 4-min intervals (0-80%). Arterial blood pressure, hindlimb blood flow, forelimb blood flow, and forelimb vascular conductance were averaged over the last minute at each level of occlusion. Stimulation of the muscle chemoreflex caused increases in arterial blood pressure and forelimb blood flow and decreases in forelimb vascular conductance. The decrease in forelimb vascular conductance demonstrates that the muscle chemoreflex causes vasoconstriction in the nonischemic exercising forelimb. Despite the decrease in vascular conductance, the increased driving pressure caused by the pressor response was large enough to produce an increased forelimb blood flow.