Fu Q, Sugiyama Y, Kamiya A, Shamsuzzaman A S, Mano T
Department of Autonomic Neuroscience, Research Institute of Environmental Medicine, Nagoya University, Nagoya 464-8601, Japan.
Am J Physiol. 1998 Oct;275(4):H1254-9. doi: 10.1152/ajpheart.1998.275.4.H1254.
To evaluate the response of vasomotor sympathetic nerve activity to lower body positive pressure (LBPP), muscle sympathetic nerve activity (MSNA) was microneurographically recorded from the tibial nerve in 10 healthy young men, along with hemodynamic variables and echocardiogram, during exposure to incremental LBPP at 10, 20, and 30 mmHg in the supine position. MSNA was suppressed to a similar extent (27%) at 10- and 20-mmHg LBPP. However, at 30-mmHg LBPP, MSNA tended to increase but was still nearly at the control value. Mean arterial pressure was elevated (11%), total peripheral resistance markedly increased (36%), and stroke volume and cardiac output tended to decrease at 30-mmHg LBPP. Heart rate remained unchanged throughout the procedures. Left atrial dimension significantly increased during 10- and 30-mmHg LBPP, indicating an increased cardiac filling. These results suggest that the inhibitory effect of the cardiopulmonary baroreflex on MSNA at 10- and 20-mmHg LBPP could be counteracted by the sympathoexcitatory effect of the intramuscular pressure-sensitive mechanoreflex at 30-mmHg LBPP. However, the increment of total peripheral resistance at 30-mmHg LBPP may not depend exclusively on this small enhancement of MSNA.
为了评估血管运动交感神经活动对下体正压（LBPP）的反应，在10名健康年轻男性仰卧位时，于10、20和30 mmHg的递增LBPP暴露期间，通过微神经图记录胫神经的肌肉交感神经活动（MSNA），同时记录血流动力学变量和超声心动图。在10 mmHg和20 mmHg的LBPP下，MSNA受到相似程度的抑制（27%）。然而，在30 mmHg的LBPP下，MSNA有增加的趋势，但仍接近对照值。在30 mmHg的LBPP下，平均动脉压升高（11%），总外周阻力显著增加（36%），每搏量和心输出量有下降趋势。在整个过程中，心率保持不变。在10 mmHg和30 mmHg的LBPP期间，左心房内径显著增加，表明心脏充盈增加。这些结果表明，在10 mmHg和20 mmHg的LBPP下，心肺压力反射对MSNA的抑制作用可能会被30 mmHg的LBPP下肌肉压力敏感机械反射的交感兴奋作用所抵消。然而，30 mmHg的LBPP下总外周阻力的增加可能不完全取决于MSNA的这种小幅度增强。
