Ray C A
Departments of Medicine and Cellular & Molecular Physiology, General Clinic Research Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Am J Physiol Heart Circ Physiol. 2000 Nov;279(5):H2399-404. doi: 10.1152/ajpheart.2000.279.5.H2399.
Muscle sympathetic nerve activity (MSNA) is altered by vestibular otolith stimulation. This study examined interactive effects of the vestibular system and baroreflexes on MSNA in humans. In study 1, MSNA was measured during 4 min of lower body negative pressure (LBNP) at either -10 or -30 mmHg with subjects in prone posture. During the 3rd min of LBNP, subjects lowered their head over the end of a table (head-down rotation, HDR) to engage the otolith organs. The head was returned to baseline upright position during the 4th min. LBNP increased MSNA above baseline during both trials with greater increases during the -30-mmHg trial. HDR increased MSNA further during the 3rd min of LBNP at -10 and -30 mmHg (Delta32% and Delta34%, respectively; P < 0.01). MSNA returned to pre-HDR levels during the 4th min of LBNP when the head was returned upright. In study 2, MSNA was measured during HDR, LBNP, and simultaneously performed HDR and LBNP. The sum of MSNA responses during individual HDR and LBNP trials was not significantly different from that observed during HDR and LBNP performed together (Delta131 +/- 28 vs. Delta118 +/- 47 units and Delta340 +/- 77 vs. Delta380 +/- 90 units for the -10 and -30 trials, respectively). These results demonstrate that vestibular otolith stimulation can increase MSNA during unloading of the cardiopulmonary and arterial baroreflexes. Also, the interaction between the vestibulosympathetic reflex and baroreflexes is additive in humans. These studies indicate that the vestibulosympathetic reflex may help defend against orthostatic challenges in humans by increasing sympathetic outflow.
肌肉交感神经活动（MSNA）会因前庭耳石刺激而改变。本研究探讨了前庭系统和压力反射对人体MSNA的交互作用。在研究1中，受试者处于俯卧姿势，在-10或-30 mmHg的下体负压（LBNP）下测量4分钟内的MSNA。在LBNP的第3分钟，受试者将头部低至桌子边缘（头低位旋转，HDR）以激活耳石器官。在第4分钟时，头部恢复到基线直立位置。在两个试验中，LBNP均使MSNA高于基线水平，在-30 mmHg试验中增加幅度更大。在-10和-30 mmHg的LBNP第3分钟时，HDR进一步增加了MSNA（分别增加32%和34%；P < 0.01）。当头部恢复直立时，LBNP第4分钟时MSNA恢复到HDR前水平。在研究2中，在HDR、LBNP以及同时进行HDR和LBNP时测量MSNA。单独的HDR和LBNP试验中MSNA反应的总和与同时进行HDR和LBNP时观察到的结果无显著差异（-10试验中分别为131±28与118±47单位，-30试验中分别为340±77与380±90单位）。这些结果表明，在前心肺和动脉压力反射卸载期间，前庭耳石刺激可增加MSNA。此外，在人体中，前庭交感反射和压力反射之间的相互作用是相加的。这些研究表明，前庭交感反射可能通过增加交感神经输出帮助人体抵御直立位挑战。
