Arterial baroreflex regulation of muscle sympathetic single unit activity in men: influence of resting blood pressure.

Arterial baroreflex regulation of muscle sympathetic single unit activity in men: influence of resting blood pressure. Am J Physiol Heart Circ Physiol. 2020 Mar 06;: Authors: Incognito AV, Samora M, Shepherd AD, Cartafina RA, Guimarães GMN, Daher M, Millar PJ, Vianna LC Abstract The arterial baroreflex has dominant control over multi-unit muscle sympathetic nerve activity (MSNA) burst occurrence but whether this extends to all single units or influenced by resting blood pressure status is unclear. In 22 men (32±8 years), we assessed 68 MSNA single units during sequential bolus injections of nitroprusside and phenylephrine (modified Oxford). Sympathetic baroreflex sensitivity (sBRS) was quantified as the weighted negative linear regression slope between diastolic blood pressure (DBP) and single unit spike firing probability and multiple spike firing. Strong negative linear relationships (r≥-0.50) between DBP and spike firing probability were observed in 63/68 (93%) single units (-2.27 ± 1.27%/cardiac cycle/mmHg [operating range: 18±8mmHg]). In contrast, only 45/68 (66%) single units had strong DBP-multiple spike firing relationships (-0.13±0.18 spikes/cardiac cycle/mmHg [operating range: 14±7mmHg]). Participants with higher resting DBP (65±3 vs. 77±3mmHg, P<0.001) had similar spike firing probability sBRS (low vs. high: -2.08±1.08 vs. -2.46±1.42%/cardiac cycle/mmHg, P=0.33), but a smaller sBRS operating range (20±6 vs....
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research