Kuipers Nathan T, Sauder Charity L, Carter Jason R, Ray Chester A
Penn State College of Medicine, The Milton S. Hershey Medical Center, Heart and Vascular Institute H047, 500 Univ. Dr., Hershey, PA 17033-2390, USA.
J Appl Physiol (1985). 2008 Apr;104(4):1129-36. doi: 10.1152/japplphysiol.01285.2007. Epub 2008 Jan 24.
The purpose of this study was to determine neurovascular responses to mental stress (MS) in the supine and upright postures. MS was elicited in 23 subjects (26 +/- 1 yr) by 5 min of mental arithmetic. In study 1 (n = 9), Doppler ultrasound was used to measure mean blood flow velocity in the renal (RBFV) and superior mesenteric arteries (SMBFV), and venous occlusion plethysmography was used to measure forearm blood flow (FBF). In study 2 (n = 14), leg blood flow (LBF; n = 9) was measured by Doppler ultrasound, and muscle sympathetic nerve activity (MSNA; n = 5) was measured by microneurography. At rest, upright posture increased heart rate and MSNA and decreased LBF, FBF, RBFV, and SMBFV and their respective conductances. MS elicited similar increases in mean arterial blood pressure ( approximately 12 mmHg) and heart rate ( approximately 17 beats/min), regardless of posture. MS in both postures elicited a decrease in RBFV, SMBFV, and their conductances and an increase in LBF, FBF, and their conductances. Changes in blood flow were blunted in the upright posture in all vascular beds examined, but the pattern of the vascular response was the same as the supine posture. MS did not change MSNA in either posture (change: approximately 1 +/- 3 and approximately 3 +/- 3 bursts/min, respectively). In conclusion, the augmented sympathetic activity of the upright posture does not alter heart rate, mean arterial blood pressure, or MSNA responses to MS. MS elicits divergent vascular responses in the visceral and peripheral vasculature. These results indicate that, although the upright posture attenuates vascular responses to MS, the pattern of neurovascular responses does not differ between postures.
本研究的目的是确定仰卧位和直立位时神经血管对精神应激（MS）的反应。通过5分钟的心算对23名受试者（26±1岁）诱发MS。在研究1（n = 9）中，使用多普勒超声测量肾动脉（RBFV）和肠系膜上动脉（SMBFV）的平均血流速度，并用静脉闭塞体积描记法测量前臂血流量（FBF）。在研究2（n = 14）中，用多普勒超声测量腿部血流量（LBF；n = 9），并用微神经ography测量肌肉交感神经活动（MSNA；n = 5）。静息时，直立位会增加心率和MSNA，并降低LBF、FBF、RBFV和SMBFV及其各自的传导率。无论体位如何，MS均会使平均动脉血压（约12 mmHg）和心率（约17次/分钟）出现类似程度的升高。两种体位下的MS均会使RBFV、SMBFV及其传导率降低，使LBF、FBF及其传导率升高。在所检查的所有血管床中，直立位时血流变化减弱，但血管反应模式与仰卧位相同。MS在两种体位下均未改变MSNA（变化分别约为1±3次/分钟和3±3次/分钟）。总之，直立位增强的交感神经活动不会改变心率、平均动脉血压或对MS的MSNA反应。MS在内脏和外周血管系统中引发不同的血管反应。这些结果表明，尽管直立位会减弱血管对MS的反应，但神经血管反应模式在不同体位之间并无差异。
