Baily R G, Prophet S A, Shenberger J S, Zelis R, Sinoway L I
Division of Cardiology, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033.
Circ Res. 1990 Jun;66(6):1720-8. doi: 10.1161/01.res.66.6.1720.
It has been postulated that cardiopulmonary baroreceptor unloading in humans results in nonuniform activation of the sympathetic nervous system. We reasoned that simultaneous measurements of arterial and venous norepinephrine (NE) spillover and clearance (using NE kinetics), muscle sympathetic neural activity (using microneurography), forearm blood flow (using plethysmography), and skin blood flow (using laser Doppler velocimetry) during lower body negative pressure at -15 mm Hg would isolate the location and extent of cardiopulmonary baroreceptor-mediated sympathetic nervous system activation. We exposed normal subjects (n = 8) to lower body negative pressure for 30 minutes, with measurements obtained at baseline, 5-10 minutes (EARLY), and 25-30 minutes (LATE). We found that arterial NE spillover, reflecting systemic sympathetic nervous system activation, did not increase significantly, whereas arterial NE clearance decreased significantly. In contrast, forearm venous NE spillover, reflecting skin and muscle sympathetic nervous system activation, increased by 17% and muscle sympathetic neural activity by 35% EARLY, whereas venous clearance did not change significantly. Although laser Doppler skin blood flow did not change, plethysmographic forearm blood flow (combined muscle and skin blood flow) decreased by 28%. All changes were sustained throughout 30 minutes of lower body negative pressure. Our data suggest that sympathetic vasoconstriction to muscle is greater than it is to skin in response to cardiopulmonary baroreceptor unloading. Moreover, our data suggest that reduced NE clearance in the arterial circulation is the primary mechanism by which arterial NE concentrations rise. Conversely, NE spillover appears to be the primary mechanism responsible for increasing venous NE concentrations measured from the forearm during cardiopulmonary baroreceptor unloading.
据推测，人体心肺压力感受器卸载会导致交感神经系统的激活不均匀。我们推断，在-15 mmHg的下体负压期间，同时测量动脉和静脉去甲肾上腺素（NE）溢出和清除率（使用NE动力学）、肌肉交感神经活动（使用微神经ography）、前臂血流量（使用体积描记法）和皮肤血流量（使用激光多普勒测速法），将能够确定心肺压力感受器介导的交感神经系统激活的位置和程度。我们让正常受试者（n = 8）接受30分钟的下体负压，在基线、5 - 10分钟（早期）和25 - 30分钟（晚期）进行测量。我们发现，反映全身交感神经系统激活的动脉NE溢出没有显著增加，而动脉NE清除率显著降低。相比之下，反映皮肤和肌肉交感神经系统激活的前臂静脉NE溢出在早期增加了17%，肌肉交感神经活动增加了35%，而静脉清除率没有显著变化。尽管激光多普勒皮肤血流量没有变化，但体积描记法测量的前臂血流量（肌肉和皮肤血流量之和）减少了28%。所有变化在30分钟的下体负压期间持续存在。我们的数据表明，在心肺压力感受器卸载时，对肌肉的交感缩血管作用大于对皮肤的作用。此外，我们的数据表明，动脉循环中NE清除率降低是动脉NE浓度升高的主要机制。相反，NE溢出似乎是心肺压力感受器卸载期间前臂测量的静脉NE浓度增加的主要机制。
