Aspirin augments carotid‐cardiac baroreflex sensitivity during muscle mechanoreflex and metaboreflex activation in older humans (875.8)

Abstract

Low‐dose aspirin augments carotid‐cardiac baroreflex (CBR‐HR) sensitivity during muscle mechanoreflex and metaboreflex activation in young humans. However, whether aspirin has a similar effect in older humans is unknown. Therefore, we examined the effect of inhibiting thromboxane (TX) A2 via low‐dose aspirin on CBR‐HR sensitivity during mechanoreflex and metaboreflex activation in older humans. Twelve older, healthy subjects (62±1y, 6 men) underwent 3min passive calf stretch (mechanoreflex) with limb occlusion after performing 1.5min 70% MVC calf exercise and post‐exercise circulatory occlusion for 3.5 min (metaboreflex). This occurred twice, after 7 days of either low‐dose (81mg) aspirin (Asp) or placebo (Pla). Asp decreased baseline TX B2 by 83±4% (P<0.05) but did not affect 6‐keto prostaglandin F1α. Resting CBR‐HR maximal gain (GMAX) was similar between Asp and Pla (‐0.18±0.05 vs. ‐0.25±0.05 b.min‐1.mmHg‐1 for Asp and Pla, respectively). CBR‐HR GMAX was significantly augmented during stretch and metabolite accumulation with Asp compared to Pla (‐0.22±0.03 vs. ‐0.15±0.02 b.min‐1.mmHg‐1 for Asp and Pla, respectively; P<0.05). These results suggest that low‐dose aspirin augments CBR‐HR sensitivity during muscle mechanoreflex and metaboreflex activation in older humans. This could be due to increased cardiac vagal activity caused by reduced TX sensitization of muscle mechanoreceptors.Grant Funding Source: Supported by NIH P01 HL096570 (LIS) and UL1 RR033184 (LIS).