A study on the role of muscle sympathetic nerve activity during movements in humans

本研究旨在阐明人类骨骼肌交感神经外流在控制随意和不随意运动的机制中的作用。1.用显微电镜记录了支配肱三头肌的胫骨神经在随意和不随意运动、各种生理性和病理性震颤时的肌肉交感神经活动（MSNA），同时记录了全身血压（BP）、肌电（emg）、肌肉紧张、局部疲劳感（LFS）和收缩肌静脉淤血。在仰卧位手部握紧和强直性手臂屈曲的自主静态运动中，随着BP、emg、肌肉张力和lfs的升高，MSNA随之增强。3.站立位时，肱三头肌和胫前肌的随意强直收缩均增强了肌内微动蛋白na，但同一肌肉的随意节律性收缩与腿部静脉池减少同时抑制了肌内微动蛋白na。当MSNA强放电时，生理性震颤（反重力肌直立性震颤和冷致颤抖）和病理性震颤（帕金森震颤和特发性震颤）都很明显。这些不自主节律运动的增加减少了腿部静脉淤积和血压升高，诱导了短暂的MSNA抑制。综上所述，骨骼肌自愿静态收缩时，MSNA增强。这种增强提高了全身血压，以维持收缩肌肉和中枢神经系统的血液流动。由于节律性运动引起的肌肉泵送效应，根据压力反射机制，随意和不随意的节律性肌肉收缩会抑制MSNA。

The present study was aimed to clarify the role of sympathetic outflow to skeletal muscles in humans in the mechanisms to control voluntary and involuntary movements. Muscle sympathetic nerve activity (MSNA) was recorded microneuro-graphically from the tibial nerve which innervated the triceps surae muscle, during voluntary and involuntary movements, different kinds of physiological and pathological tremors, simultaneously with systemic blood pressure (BP), electromyo-grams (EMGs), muscle tension, local fatigue sensation (LFS) and venous pooling of the contracting muscles.1.During voluntary static exercise of hand gripping and tonic flexion of the arm in supine position, MSNA was enhanced in accordance with the increase in BP,EMGs, muscle tension and LFS.2.MSNA in standing position was enhanced during voluntary tonic contraction of both the triceps surae muscle and the tibialis anterior muscle, but was suppressed by voluntary rhythmic contraction of the same muscles concomitantly with the reduction in the venous pooling in the leg.3.Both physiological tremors (orthostatic tremor in antigravity muscle and cold-induced shivering) and pathological tremors (Parkinsonian tremor and essential tremor) were apparent when MSNA was strongly discharged. The increase of these involuntary rhythmic movements reduced venous pooling in the leg and elevated BP,inducing transient suppression of MSNA.In conclusion, MSNA is enhanced during voluntary static contraction of the skeletal muscles. This enhancement elevates systemic blood pressure to maintain the blood flow in the contracting muscle and the central nervous system. MSNA is rather suppressed by voluntary and involuntary rhythmic muscle contraction depending on baroreflex mechanisms due presumably to muscle pumping effects induced by rhythmic movements.