Sympathetic arterial baroreflex hysteresis in humans: different patterns during low and high pressure levels.

Sympathetic arterial baroreflex hysteresis in humans: different patterns during low and high pressure levels. Am J Physiol Heart Circ Physiol. 2020 Aug 28;: Authors: Incognito AV, Samora M, Shepherd AD, Cartafina RA, Guimarães GMN, Daher M, Vianna LC, Millar PJ Abstract Fluctuations in diastolic pressure modulates muscle sympathetic nerve activity (MSNA) through the arterial baroreflex. A higher sympathetic baroreflex sensitivity (sBRS) to pressure falls compared to rises has been reported, however, the underlying mechanisms are unclear. We assessed whether beat-to-beat falling and rising diastolic pressures operate on two distinct baroreflex response curves. Twenty-two men (32±8 years) underwent sequential bolus injections of nitroprusside and phenylephrine (modified Oxford test) with continuous recording of heart rate, blood pressure, and MSNA. The weighted negative linear regression slope between falling or rising diastolic pressure and MSNA burst incidence quantified sBRSfall and sBRSrise, respectively. The diastolic pressure evoking a MSNA burst incidence of 50 (T50) was calculated. sBRSfall was greater than sBRSrise (-6.24±2.80 vs. -4.34±2.16 bursts/100 heartbeats/mmHg, P=0.01) and had a narrower operating range (14±8 vs. 20±10 mmHg, P=0.01) that was shifted rightward (T50: 75±9 and 70±11 mmHg, P<0.001). At diastolic pressures below baseline, sBRSfall was less than sBRSrise (-1.81±1.31 vs. -3.59±1.70 bursts/100 hea...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research