Nardone Massimo, Katerberg Carlin, Teixeira André L, Lee Jordan B, Bommarito Julian C, Millar Philip J
Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, Canada.
Am J Physiol Regul Integr Comp Physiol. 2022 Jun 1;322(6):R620-R628. doi: 10.1152/ajpregu.00034.2022. Epub 2022 Apr 26.
Sympathetic transduction of blood pressure (BP) is correlated negatively with resting muscle sympathetic nerve activity (MSNA) in cross-sectional data, but the acute effects of increasing MSNA are unclear. Sixteen (4 female) healthy adults (26 ± 3 years) underwent continuous measurement of heart rate, BP, and MSNA at rest and during graded lower body negative pressure (LBNP) at -10, -20, and -30 mmHg. Sympathetic transduction of BP was quantified in the time (signal averaging) and frequency (MSNA-BP gain) domains. The proportions of MSNA bursts firing within each tertile of BP were calculated. As expected, LBNP increased MSNA burst frequency ( < 0.01) and burst amplitude ( < 0.02), although the proportions of MSNA bursts firing across each BP tertile remained stable (all > 0.44). The MSNA-diastolic BP low-frequency transfer function gain ( = 0.25) was unchanged during LBNP; the spectral coherence was increased ( = 0.03). Signal-averaged sympathetic transduction of diastolic BP was unchanged (from 2.1 ± 1.0 at rest to 2.4 ± 1.5, 2.2 ± 1.3, and 2.3 ± 1.4 mmHg; = 0.43) during LBNP, but diastolic BP responses following nonburst cardiac cycles progressively decreased (from -0.8 ± 0.4 at rest to -1.0 ± 0.6, -1.2 ± 0.6, and -1.6 ± 0.9 mmHg; < 0.01). As a result, the difference between MSNA burst and nonburst diastolic BP responses was increased (from 2.9 ± 1.4 at rest to 3.4 ± 1.9, 3.4 ± 1.9, and 3.9 ± 2.1 mmHg; < 0.01). In conclusion, acute increases in MSNA using LBNP did not alter traditional signal-averaged or frequency-domain measures of sympathetic transduction of BP or the proportion of MSNA bursts firing at different BP levels. The factors that determine changes in the firing of MSNA bursts relative to oscillations in BP require further investigation.
在横断面数据中，血压（BP）的交感神经传导与静息肌肉交感神经活动（MSNA）呈负相关，但MSNA增加的急性效应尚不清楚。16名（4名女性）健康成年人（26±3岁）在静息状态下以及在-10、-20和-30 mmHg的分级下肢负压（LBNP）期间，连续测量心率、血压和MSNA。在时间（信号平均）和频率（MSNA-BP增益）域中对BP的交感神经传导进行量化。计算每个血压三分位数内MSNA爆发放电的比例。正如预期的那样，LBNP增加了MSNA爆发频率（<0.01）和爆发幅度（<0.02），尽管在每个血压三分位数上MSNA爆发放电的比例保持稳定（均>0.44）。在LBNP期间，MSNA-舒张压低频传递函数增益（=0.25）未改变；频谱相干性增加（=0.03）。在LBNP期间，舒张压的信号平均交感神经传导未改变（从静息时的2.1±1.0变为2.4±1.5、2.2±1.3和2.3±1.4 mmHg；=0.43），但非爆发性心动周期后的舒张压反应逐渐降低（从静息时的-0.8±0.4变为-1.0±0.6、-1.2±0.6和-1.6±0.9 mmHg；<0.01）。结果，MSNA爆发和非爆发性舒张压反应之间的差异增加（从静息时的2.9±1.4变为3.4±1.9、3.4±1.9和3.9±2.1 mmHg；<0.01）。总之，使用LBNP急性增加MSNA不会改变传统的信号平均或频域测量的BP交感神经传导，也不会改变在不同血压水平上MSNA爆发放电的比例。相对于血压振荡，决定MSNA爆发放电变化的因素需要进一步研究。
