Hennig R, Lømo T
Acta Physiol Scand. 1987 May;130(1):115-31. doi: 10.1111/j.1748-1716.1987.tb08118.x.
This study seeks to identify the mechanisms which motoneurones use to control the contractile force and speed of skeletal muscles. We have stimulated directly slow soleus (SOL) and fast extensor digitorum longus (EDL) muscles of adult rats intermittently at 100 Hz for 1-9 months. The muscles were either chronically denervated, denervated and reinnervated, or normally innervated. The stimulation started either immediately, or more commonly, after 1-9 months of denervation. Stimulation starting several months after denervation increased the mean maximum tetanic tension 37 times in SOL and eight times in EDL. These values represented 40 and 12% of the increases obtained by reinnervation after comparable periods of time. In denervated SOL and EDL muscles stimulated directly for more than 2 months, the mean isometric twitch contraction times were 13 and 12.7 ms, as in normal EDL muscles (13 ms). In innervated SOL muscles stimulated directly for 1-4 months, the mean twitch contraction times were 23.6 ms (normally innervated) and 19.2 ms (reinnervated), which were considerably shorter than in normal control SOL muscles (39.2 ms). Single motor unit recordings revealed that the natural (background) nerve impulse activity was essentially unaffected by the stimulation. Twitch contraction time and percentage of type II fibres in SOL muscles were related. The fastest muscles (denervated and stimulated) consisted of 100% type II fibres (with one exception), the second fastest (reinnervated and stimulated) of 70-50%, the third fastest (normally innervated and stimulated) of 45-0%, the second slowest (reinnervated) of 15-0%, and the slowest muscles (innervated controls) of 5-0% type II fibres.
本研究旨在确定运动神经元用于控制骨骼肌收缩力和速度的机制。我们以100Hz的频率间歇性刺激成年大鼠的慢比目鱼肌（SOL）和快趾长伸肌（EDL）1至9个月。这些肌肉分别处于慢性去神经、去神经后再神经支配或正常神经支配状态。刺激要么立即开始，要么更常见的是在去神经1至9个月后开始。去神经数月后开始的刺激使SOL的平均最大强直张力增加了37倍，EDL增加了8倍。这些值分别相当于相同时间段再神经支配后增加量的40%和12%。直接刺激去神经的SOL和EDL肌肉超过2个月，其平均等长单收缩时间分别为13ms和12.7ms，与正常EDL肌肉（13ms）相同。直接刺激神经支配的SOL肌肉1至4个月，其平均单收缩时间分别为23.6ms（正常神经支配）和19.2ms（再神经支配），明显短于正常对照SOL肌肉（39.2ms）。单运动单位记录显示，自然（背景）神经冲动活动基本不受刺激影响。SOL肌肉的单收缩时间与II型纤维百分比相关。最快的肌肉（去神经并受刺激）由100%的II型纤维组成（有一个例外），第二快的（再神经支配并受刺激）为70 - 50%，第三快的（正常神经支配并受刺激）为45 - 0%，第二慢的（再神经支配）为15 - 0%，最慢的肌肉（神经支配对照）为5 - 0%的II型纤维。
