Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.
Catholic University of Santos, São Paulo, Brazil.
Am J Physiol Regul Integr Comp Physiol. 2024 Dec 1;327(6):R590-R600. doi: 10.1152/ajpregu.00112.2024. Epub 2024 Oct 22.
Despite some evidence, the role of sympathetic nerve activity in the regulation of cerebral blood flow remains controversial. In humans, muscle sympathetic nervous activity (MSNA) is the only direct measure of sympathetic nerve activity that can be recorded with sufficient temporal resolution to allow association with dynamic regulation of cerebral blood velocity (CBv). This study tested the hypothesis that MSNA is associated with the regulation of CBv at rest and during different physiological maneuvers. Nine healthy subjects underwent two sympathoexcitatory maneuvers: ) isometric handgrip exercise (HGR), and ) cold pressor test (CPT). Mean arterial pressure (MAP; oscillometric method), CBv (transcranial Doppler ultrasound), and MSNA (microneurography) were measured continuously during experimental protocols. Ordinary and partial coherences of the MAP, CBv, and MSNA time series were estimated by transfer function analysis in the low-frequency range (0.07-0.20 Hz), using MAP and MSNA as inputs and CBv as the output variable. When the influence of MSNA was taken into account, the partial coherences between MAP and CBv were considerably reduced at baseline ( < 0.01), HGR ( = 0.02), and CPT ( < 0.01). Similarly, when the influence of MAP was taken into account, the coherence between MSNA and CBv was considerably reduced at baseline ( < 0.01), HGR ( = 0.02), and CPT ( = 0.01), leading to the conclusion, that MSNA was associated to dynamic regulation of CBv. Partial coherence analysis is a promising method for assessing the influence of the sympathetic nervous system on cerebral hemodynamics. Partial coherence analysis has been instrumental in demonstrating, for the first time, that cerebral blood velocity (CBv) is continuously influenced, not only by fluctuations in mean arterial pressure but also muscle sympathetic nervous activity (MSNA), leading to similar dynamic responses at rest and during different sympathoexcitatory maneuvers in healthy subjects. Modeling the temporal relationship between MSNA and CBv opens new opportunities for advancing knowledge regarding the role of the sympathetic nervous system in the regulation of cerebral circulation in health and disease.
尽管有一些证据，但交感神经活动在调节脑血流中的作用仍然存在争议。在人类中，肌肉交感神经活动（MSNA）是唯一可以用足够的时间分辨率记录的交感神经活动的直接测量指标，从而可以与脑血流速度（CBV）的动态调节相关联。本研究检验了以下假设：MSNA 与休息时和不同生理操作期间的 CBV 调节有关。9 名健康受试者接受了两种交感兴奋操作：）等长握力运动（HGR），和）冷加压试验（CPT）。在实验方案期间，使用振荡法测量平均动脉压（MAP）、CBV（经颅多普勒超声）和 MSNA（微神经记录）的连续测量值。通过传递函数分析，在低频范围（0.07-0.20 Hz）中估计 MAP、CBV 和 MSNA 时间序列的普通和偏相干性，使用 MAP 和 MSNA 作为输入，CBV 作为输出变量。当考虑到 MSNA 的影响时，MAP 和 CBV 之间的偏相干性在基线时显著降低（<0.01），HGR 时（=0.02），CPT 时（<0.01）。同样，当考虑到 MAP 的影响时，MSNA 和 CBV 之间的相干性在基线时显著降低（<0.01），HGR 时（=0.02），CPT 时（=0.01），这表明 MSNA 与 CBV 的动态调节有关。偏相干分析是评估交感神经系统对脑血流动力学影响的一种很有前途的方法。偏相干分析首次证明，脑血流速度（CBV）不仅受到平均动脉压波动的影响，而且还受到肌肉交感神经活动（MSNA）的影响，导致在健康受试者的休息时和不同的交感兴奋操作期间产生类似的动态反应。对 MSNA 和 CBV 之间的时间关系进行建模为了解交感神经系统在健康和疾病状态下调节脑循环中的作用提供了新的机会。
