Muscle metaboreflex activation during dynamic exercise evokes epinephrine release resulting in β2-mediated vasodilation.

Muscle metaboreflex activation during dynamic exercise evokes epinephrine release resulting in β2-mediated vasodilation. Am J Physiol Heart Circ Physiol. 2014 Dec 24;:ajpheart.00648.2014 Authors: Kaur J, Spranger MD, Hammond RL, Krishnan AC, Alvarez A, Augustyniak RA, O'Leary DS Abstract Muscle metaboreflex-induced increases in mean arterial pressure (MAP) during submaximal dynamic exercise are mediated principally by increases in cardiac output. To what extent, if any, the peripheral vasculature contributes to this rise in MAP is debatable. In several studies, we observed that in response to muscle metaboreflex activation (MMA; induced by partial hindlimb ischemia) a small but significant increase in vascular conductance occurred within the non-ischemic areas (calculated as cardiac output minus hindlimb blood flow and termed non-ischemic vascular conductance; NIVC). We hypothesized that these increases in NIVC may stem from a metaboreflex-induced release of epinephrine resulting in β2-mediated dilation. We measured NIVC and arterial plasma epinephrine levels in chronically instrumented dogs during rest, mild exercise (3.2 kph) and MMA before and after β-blockade (propanolol; 2 mg/kg), α1-blockade (prazosin; 50 µg/kg) and α1+β-blockade. Both epinephrine and NIVC increased significantly from exercise to MMA: 81.9 ± 18.6 to 141.3 ± 22.8 pg/ml and 33.8 ± 1.5 to 37.6 ± 1.6 ml/min/mmHg, respectively. These metaboreflex-induced ...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research