Modulation of the control of muscle sympathetic nerve activity during severe orthostatic stress
Modulation of the control of muscle sympathetic nerve activity during severe orthostatic stress
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DOI：
10.1113/jphysiol.2006.117507
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发表时间：
2006-11-01
影响因子：
5.5
通讯作者：
Nishiyasu, Takeshi
中科院分区：
文献类型：
--
作者：
Ichinose, Masashi;Saito, Mitsuru;Nishiyasu, Takeshi
我们测试的假设，动脉压力感受性反射（ABR）介导的心跳控制肌肉交感神经活动（MSNA）进行性调制的直立性压力增加在人类，但这种控制成为受损的直立性晕厥发作之前。在17名健康受试者中，通过分析仰卧位休息（对照）和进行性运动期间舒张压（DAP）的搏动间自发变化与MSNA之间的关系，逐步增加下体负压（LBNP），每5分钟增加-10 mmHg，直至晕厥前期（9例受试者）或达到-60 mmHg。(1)DAP和爆破强度之间以及DAP和总MSNA之间的线性关系随着LBNP增加而逐渐向上移动，直到发生晕厥的水平。然而，DAP和爆裂发生率之间的关系从仅对照组逐渐向上移动到LBNP = -30 mmHg;在较高LBNP下没有进一步向上移动。(2)尽管在所有检测的LBNP下，DAP与爆发强度之间以及DAP与总MSNA之间的关系的斜率保持恒定，但发生晕厥的水平除外，但在LBNP为-40 mmHg或更高时（与对照组相比），DAP与爆发发生率之间的关系的斜率降低。(3)在晕厥受试者中，DAP与爆发发生率、爆发强度和总MSNA之间关系的斜率在晕厥发作前1-2分钟内均显著降低。综上所述，这些结果表明，随着直立性应激的增加，对MSNA的压力反射控制逐渐受到调节，因此，在与直立性晕厥相关的严重低血压发生前的一段时间内，其敏感性大幅降低。
We tested the hypothesis that arterial baroreflex (ABR)-mediated beat-to-beat control over muscle sympathetic nerve activity (MSNA) is progressively modulated as orthostatic stress increases in humans, but that this control becomes impaired just before the onset of orthostatic syncope. In 17 healthy subjects, the ABR control over MSNA (burst incidence, burst strength and total MSNA) was evaluated by analysing the relationship between beat-to-beat spontaneous variations in diastolic blood pressure (DAP) and MSNA during supine rest (control) and during progressive, stepwise increases in lower body negative pressure (LBNP) that were incremented by -10 mmHg every 5 min until presyncope (nine subjects) or -60 mmHg was reached. (1) The linear relationships between DAP and burst strength and between DAP and total MSNA were shifted progressively upward as LBNP increased until the level at which syncope occurred. The relationship between DAP and burst incidence, however, gradually shifted upward from control only to LBNP = -30 mmHg; there was no further upward shift at higher LBNPs. (2) Although the slope of the relationship between DAP and burst strength and between DAP and total MSNA remained constant at all LBNPs tested, except at the level where syncope occurred, the slope of the relationship between DAP and burst incidence was reduced at LBNPs of -40 mmHg and higher (versus control). (3) In syncopal subjects, the slopes of the relationships between DAP and burst incidence, burst strength, and total MSNA were all substantially reduced during the 1-2 min period prior to the onset of syncope. Taken together, these results suggest baroreflex control over MSNA is progressively modulated as orthostatic stress increases, so that its sensitivity is substantially reduced during the period immediately preceding the severe hypotension associated with orthostatic syncope.