Earlier reports suggest that limb venous distension evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) (i.e., venous distension reflex). Our recent report also shows that suction of arterially occluded limb evokes venous distension reflex. We postulate that the venous distension reflex contributes to autonomic responses to orthostatic stress. In this study, we hypothesized that orthostatic tolerance would be linked to the MSNA response seen with lower limb suction. Fifteen healthy subjects were tested in the supine position. Negative pressure (-100 mmHg) was applied on an arterially occluded lower limb for 2 min. MSNA from the peroneal nerve in the limb not exposed to suction, ECG, and BP (Finometer) was recorded throughout the study. Limb occlusion without suction was used as a control trial. In a separate visit, the individual's orthostatic tolerance was assessed using a graded lower body negative pressure (LBNP) tolerance test. Mean arterial BP and MSNA (18.6 ± 1.9 to 23.6 ± 2.0 bursts/min) significantly (both P < 0.05) increased during limb suction. Orthostatic tolerance index positively correlated (R = 0.636, P = 0.011) with the MSNA response seen with suction during occlusion. Since the venous distension reflex strength correlates with the level of orthostatic tolerance, we speculate that lower-limb venous distension reflex engagement increases the sympathetic responses during orthostatic challenge and serves to maintain BP with postural stress.

中文翻译：

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年轻健康人的下肢静脉扩张反射和直立耐受性。

较早的报告表明，肢体静脉扩张会引起肌肉交感神经活动 (MSNA) 和血压 (BP)（即静脉扩张反射）的反射性增加。我们最近的报告还表明，动脉闭塞肢体的抽吸会引起静脉扩张反射。我们假设静脉扩张反射有助于对直立压力的自主反应。在这项研究中，我们假设直立耐受性与下肢抽吸所见的 MSNA 反应有关。15 名健康受试者在仰卧位进行测试。对动脉闭塞的下肢施加负压 (-100 mmHg) 2 分钟。在整个研究过程中记录来自未暴露于抽吸的肢体腓神经的 MSNA、ECG 和 BP（Finometer）。没有抽吸的肢体闭塞被用作对照试验。在单独的访问中，使用分级下体负压 (LBNP) 耐受性测试评估个体的直立耐受性。在肢体抽吸过程中，平均动脉血压和 MSNA（18.6 ± 1.9 至 23.6 ± 2.0 次/分钟）显着增加（均 P < 0.05）。直立耐受指数正相关（R = 0.636，P = 0.011）与在闭塞期间用抽吸观察到的 MSNA 反应。由于静脉扩张反射强度与直立耐受水平相关，我们推测下肢静脉扩张反射参与增加直立挑战期间的交感神经反应，并有助于通过体位压力维持血压。0 次/分钟）在肢体抽吸过程中显着增加（均 P < 0.05）。直立耐受指数正相关（R = 0.636，P = 0.011）与在闭塞期间用抽吸观察到的 MSNA 反应。由于静脉扩张反射强度与直立耐受水平相关，我们推测下肢静脉扩张反射参与增加直立挑战期间的交感神经反应，并有助于通过体位压力维持血压。0 次/分钟）在肢体抽吸过程中显着增加（均 P < 0.05）。直立耐受指数正相关（R = 0.636，P = 0.011）与在闭塞期间用抽吸观察到的 MSNA 反应。由于静脉扩张反射强度与直立耐受水平相关，我们推测下肢静脉扩张反射参与增加直立挑战期间的交感神经反应，并有助于通过体位压力维持血压。