Bawa Parveen, Chalmers Gordon
School of Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Muscle Nerve. 2008 Dec;38(6):1604-15. doi: 10.1002/mus.21184.
This study was designed to extend to humans the findings of classical studies on anesthetized cats, which have examined the discharge of spinal motoneurons in response to high-frequency stimulus trains delivered to Ia afferents. Experiments were conducted on the monosynaptic pathway in the flexor carpi radialis (FCR) and soleus muscles. Subjects maintained a rhythmic discharge of a single motor unit (SMU) in either the FCR or soleus while homonymous Ia afferents were stimulated with either a single- or multipulse train. An n@IPI stimulus train had n pulses (n = 2-4) and an interpulse interval (IPI) of 1-8 ms. For each condition and motor unit, surface electromyographic (EMG) activity was averaged, and peristimulus-time histograms (PSTHs) were constructed for the SMU. The magnitude of the EMG was high for IPI = 1 ms, low for IPI = 2-3 ms, and high for IPI = 4-8 ms. SMU responses showed a similar pattern, which indicated that the increased EMG response was due to the presence of multiple peaks in a PSTH. The key results indicate that: (1) a short, high-frequency stimulus train enhances the discharge probability of a motoneuron above that observed with a single pulse; and (2) the increased motoneuron responses are significantly greater for the FCR than for the soleus muscle.
本研究旨在将关于麻醉猫的经典研究结果扩展至人类，这些经典研究检测了脊髓运动神经元对传递至Ia传入纤维的高频刺激串的放电反应。实验在桡侧腕屈肌（FCR）和比目鱼肌的单突触通路中进行。当用单脉冲或多脉冲串刺激同名Ia传入纤维时，受试者保持FCR或比目鱼肌中单个运动单位（SMU）的节律性放电。n@IPI刺激串有n个脉冲（n = 2 - 4），脉冲间隔（IPI）为1 - 8毫秒。对于每种条件和运动单位，对表面肌电图（EMG）活动进行平均，并为SMU构建刺激后时间直方图（PSTH）。当IPI = 1毫秒时，EMG幅度较高；当IPI = 2 - 3毫秒时，幅度较低；当IPI = 4 - 8毫秒时，幅度较高。SMU反应呈现出类似模式，这表明EMG反应增强是由于PSTH中存在多个峰值。关键结果表明：（1）短的高频刺激串会提高运动神经元的放电概率，使其高于单脉冲刺激时观察到的放电概率；（2）FCR运动神经元反应的增加幅度明显大于比目鱼肌。
