Rotshenker S, McMahan U J
J Neurocytol. 1976 Dec;5(6):719-30. doi: 10.1007/BF01181583.
The pattern of reinnervation of muscle fibres after a nerve crush was examined in the cutaneous pectoris muscle of the frog by microscopy and electrophysiology. Normally, about 16% of the muscle fibres are innervated by more than one motor neuron. Two months after reinnervation, about 50% of the fibres are polyneuronally innervated and this high incidence persists for at least seven months. The total number of neurons reinnervating the muscle, as well as the number of muscle fibres comprising the muscle, are normal. However, nerve fibres sprout branches at the site of the crush, and, therefore, the number of axons entering the muscle is greater than normal. Regenerating axons contact muscle fibres precisely at the original synaptic sites and the terminal branches from different axons that end on the same muscle fibre often run side by side occupying stretches or original postsynaptic membrane normally covered by one terminal. Our findings indicate that the amount of synaptic contact during regeneration is limited by the amount of original postsynaptic membrane and that any number of axons that reach vacant portions of original postsynaptic membrane can make synaptic contact with it. Surprisingly, control cutaneous pectoris muscles, situated contralaterally to those that were denervated, also exhibited an abnormal pattern of innervation. Although neither nerve nor muscle was disturbed by the operation, there was a higher incidence of polyneuronal innervation (27% vs 16%) than in muscles of normal animals.
通过显微镜检查和电生理学方法，对青蛙胸皮肌神经挤压后肌纤维的再支配模式进行了研究。正常情况下，约16%的肌纤维由一个以上的运动神经元支配。再支配两个月后，约50%的纤维接受多神经元支配，且这种高发生率至少持续七个月。重新支配肌肉的神经元总数以及构成该肌肉的肌纤维数量均正常。然而，神经纤维在挤压部位会萌发出分支，因此进入肌肉的轴突数量多于正常情况。再生轴突精确地在原来的突触部位与肌纤维接触，并且来自不同轴突的终末分支在同一肌纤维上往往并行排列，占据了通常由一个终末覆盖的一段或原来的突触后膜。我们的研究结果表明，再生过程中突触接触的数量受原来突触后膜数量的限制，并且任何到达原来突触后膜空缺部分的轴突数量都可以与之形成突触接触。令人惊讶的是，与去神经支配的肌肉相对侧的对照胸皮肌也表现出异常的支配模式。尽管手术对神经和肌肉均未造成干扰，但与正常动物的肌肉相比，多神经元支配的发生率更高（27%对16%）。
