Regulation of muscle sympathetic nerve activity after bed rest deconditioning.
Regulation of muscle sympathetic nerve activity after bed rest deconditioning.
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卧床休息后肌肉交感神经活动的调节。
DOI：
10.1152/ajpheart.2001.280.5.h2230
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Levine,BD
中科院分区：
文献类型：
--
作者：
Pawelczyk,JA;Zuckerman,JH;Blomqvist,CG;Levine,BD
心血管去调理降低立位耐受性。为了确定自主神经功能的改变是否可能产生这种影响，我们对7名受试者在−6°头低位卧床18天前后绘制了肢体血管阻力、肌交感神经活动和肺毛细血管楔压的刺激-反应曲线。下体负压(−15和−30 mm Hg)和快速输注生理盐水(15和30ml/kg体重)均可产生较大幅度的PCWP。立位耐力由LBNP评分评估至晕厥前。卧床休息使下体负压耐量分别从23.9±2.1分钟降至21.2±1.5分钟(均值±SE，P=0.02)。卧床后MSNA-PCWP关系不变，尽管在LBNP方案的任何阶段PCWP较低，MSNA较大。因此，卧床休息解除条件反射导致低血容量，导致刺激反应曲线上操作点的移位。卧床后肢体血管阻力与MSNA的关系无明显变化。我们的结论是，卧床休息解除条件不会改变MSNA的反射控制，但可能会通过低血容量和心脏萎缩的组合产生立位不耐受。
Cardiovascular deconditioning reduces orthostatic tolerance. To determine whether changes in autonomic function might produce this effect, we developed stimulus-response curves relating limb vascular resistance, muscle sympathetic nerve activity (MSNA), and pulmonary capillary wedge pressure (PCWP) with seven subjects before and after 18 days of −6° head-down bed rest. Both lower body negative pressure (LBNP; −15 and −30 mmHg) and rapid saline infusion (15 and 30 ml/kg body wt) were used to produce a wide variation in PCWP. Orthostatic tolerance was assessed with graded LBNP to presyncope. Bed rest reduced LBNP tolerance from 23.9 ± 2.1 to 21.2 ± 1.5 min, respectively (means ± SE,P= 0.02). The MSNA-PCWP relationship was unchanged after bed rest, though at any stage of the LBNP protocol PCWP was lower, and MSNA was greater. Thus bed rest deconditioning produced hypovolemia, causing a shift in operating point on the stimulus-response curve. The relationship between limb vascular resistance and MSNA was not significantly altered after bed rest. We conclude that bed rest deconditioning does not alter reflex control of MSNA, but may produce orthostatic intolerance through a combination of hypovolemia and cardiac atrophy.