P2X receptor blockade attenuates the sympathetic response to exercise in humans

Abstract

Animal studies suggest that ATP may play a role in evoking the muscle reflex via stimulating P2X receptors on sensory neurons. No data about the role of P2X receptors in the muscle pressor reflex in humans has been reported. We hypothesized that P2X receptor blockade attenuates the exercise pressor response in humans. Blood pressure (Finometer), heart rate, and muscle sympathetic nerve activity (MSNA) from peroneal nerve were assessed during fatiguing isometric handgrip, post exercise muscle ischemia (PEMI), and passive muscle stretch during PEMI in 8 young healthy volunteers. The protocol was performed before and after local infusion of vitamin B6 (Pyridoxine Hydrochloride, a non‐specific blocker of P2 receptors) in saline via Bier block. In the second experiment, the same amount of saline was infused via the Bier block. After Vitamin B6, the MSNA responses to fatiguing handgrip (Δ342±78 vs. Δ548±102), PEMI (Δ280±43 vs. Δ451±85) and passive stretch (Δ338±62 vs. Δ559±107 units/min, all P<0.05) were significantly less than those before B6. The blood pressure responses were also significantly (all P<0.05) less than those before B6. Saline Bier block had no similar effects on the MSNA and blood pressure responses. These data verified our hypothesis that P2X receptor blockade attenuates the exercise pressor response in humans. Supported by AHA 0635245 N, NIH P01 HL077670, and M01 RR010732.