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

本研究的目的是阐明交感神经流出到骨骼肌在人类的机制，以控制自愿和不自愿的运动中的作用。用显微神经摄影技术记录支配小腿三头肌的胫神经在随意运动和不随意运动、各种生理性和病理性震颤时的肌交感神经活动（MSNA），同时记录全身血压（BP）、肌电图（EMG）、肌张力、局部疲劳感（LFS）和收缩肌肉的静脉汇集1.在仰卧位的手抓握和手臂强直屈曲的自愿静态锻炼期间，MSNA随血压、肌电、肌张力和LFS的增加而增强。2.立位时小腿三头肌和胫骨前肌自主紧张性收缩时MSNA增强，但是，随着腿部静脉汇集减少，同一肌肉的自主节律性收缩抑制了这种作用。当MSNA强烈释放时，生理性震颤（反重力肌的直立性震颤和冷诱导的颤抖）和病理性震颤（帕金森震颤和特发性震颤）明显。这些不自主的节奏性运动的增加减少了腿部的静脉汇集和血压升高，引起MSNA的短暂抑制。总之，MSNA在骨骼肌的自愿静态收缩过程中增强。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中的血流。MSNA被自主和非自主的节律性肌肉收缩抑制，这取决于压力反射机制，可能是由于节律性运动诱导的肌肉泵送效应。

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.