School of Applied Physiology, Georgia Institute of Technology, Atlanta, Georgia;
School of Applied Physiology, Georgia Institute of Technology, Atlanta, Georgia; Department of Physical Therapy, Georgia State University, Atlanta, Georgia; and Rehabilitation R&D Center of Excellence, Atlanta Department of Veterans Affairs Medical Center, Decatur, Georgia.
J Neurophysiol. 2014 Jun 15;111(12):2656-64. doi: 10.1152/jn.00778.2013. Epub 2014 Mar 26.
Unloading of the baroreceptors due to orthostatic stress increases corticospinal excitability. The purpose of this study was to examine the effects of baroreceptor unloading due to orthostatic stress on intracortical excitatory and inhibitory pathways in the motor cortex. With transcranial magnetic stimulation, measures of intracortical excitability for a hand muscle were tested on 2 days in healthy young adults. Lower body negative pressure (LBNP) of 40 mmHg was applied during one of the days and not during the Control day. During application of LBNP heart rate and the low-frequency component of heart rate variability increased, while mean arterial blood pressure was maintained. In the resting state, LBNP decreased short-interval intracortical inhibition (SICI) and had no effect on intracortical facilitation (ICF) or short-interval intracortical facilitation (SICF) compared with the Control day. During isometric contraction, no effects of LBNP were observed on tested measures of intracortical excitability including SICI, SICF, and cortical silent period. It was concluded that baroreceptor unloading due to orthostatic stress results in diminished intracortical inhibition, at least in the resting muscle.
由于体位性应激导致的压力感受器卸载会增加皮质脊髓兴奋性。本研究旨在探讨体位性应激导致的压力感受器卸载对运动皮质内皮质兴奋性和抑制性通路的影响。在健康的年轻成年人中，使用经颅磁刺激在 2 天内测试手部肌肉的皮质内兴奋性测量值。在其中一天应用 40mmHg 的下体负压（LBNP），而在对照日不应用。在 LBNP 应用期间，心率和心率变异性的低频成分增加，而平均动脉血压保持不变。在静息状态下，与对照日相比，LBNP 降低了短间隔皮质内抑制（SICI），但对皮质内易化（ICF）或短间隔皮质内易化（SICF）没有影响。在等长收缩期间，LBNP 对测试的皮质内兴奋性测量值（包括 SICI、SICF 和皮质静息期）没有影响。结论是，由于体位性应激导致的压力感受器卸载会导致皮质内抑制减弱，至少在休息状态下的肌肉中是这样。
