Farina Dario, Pozzo Marco, Lanzetta Marco, Enoka Roger M
Department of Health Science and Technology, Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark.
J Neurophysiol. 2008 May;99(5):2232-40. doi: 10.1152/jn.01273.2007. Epub 2008 Mar 5.
The study analyzed the discharge characteristics of the motor units in an intrinsic muscle of a transplanted hand. Multichannel electromyographic (EMG) recordings were obtained in 11 experimental sessions over 16 mo starting from day 205 after a hand was transplanted in a 35-yr-old man who had lost his right hand 22 yr earlier. The action potentials discharged by single motor units were identified from the surface EMG signals of the abductor digiti minimi muscle in the transplanted hand as the individual performed 60-s maximal and linearly increasing (ramp) contractions. Discharge rate decreased from 27.1 +/- 8.4 pulses per second (pps) at the start of the maximal contractions to 17.2 +/- 2.9 pps at the end (P < 0.001) and increased from 17.4 +/- 4.3 to 22.1 +/- 5.0 pps during the ramp contractions (P < 0.05). The SD of the interspike interval (ISI) nearly related to the mean ISI with a similar regression slope for the maximal (0.49 +/- 0.09) and ramp contractions (0.43 +/- 0.10). The coefficient of variation for ISI was higher than values in able-bodied persons and did not change during either the maximal (36.8 +/- 10.8%) or the ramp contractions (35.9 +/- 7.4%). High-frequency bursts of activity with <20 ms between two and six action potentials occurred during both maximal and ramp contractions. In conclusion, motor neurons that reinnervated a muscle in a transplanted hand discharged action potentials with a high degree of variability that suggested greater synaptic noise during the voluntary contractions.
该研究分析了移植手固有肌中运动单位的放电特性。在一名35岁男性（其右手在22年前丧失）接受手部移植后205天起的16个月内，进行了11次实验性记录，获取多通道肌电图（EMG）。当个体进行60秒的最大收缩和线性递增（斜坡）收缩时，从移植手小指展肌的表面EMG信号中识别出单个运动单位发放的动作电位。放电频率从最大收缩开始时的27.1±8.4次/秒降至结束时的17.2±2.9次/秒（P<0.001），并在斜坡收缩期间从17.4±4.3次/秒增加至22.1±5.0次/秒（P<0.05）。峰间期（ISI）的标准差与平均ISI密切相关，最大收缩（0.49±0.09）和斜坡收缩（0.43±0.10）的回归斜率相似。ISI的变异系数高于健全人，在最大收缩（36.8±10.8%）或斜坡收缩（35.9±7.4%）期间均未改变。在最大收缩和斜坡收缩期间均出现了两到六个动作电位之间间隔<20毫秒的高频爆发活动。总之，重新支配移植手肌肉的运动神经元发放动作电位具有高度变异性，这表明在自主收缩期间存在更大的突触噪声。
