Hopkins W G, Brown M C
Neuroscience. 1982 Jan;7(1):37-44. doi: 10.1016/0306-4522(82)90151-8.
The right gluteus maximus muscles of young adult mice were paralysed with botulinum toxin for up to 21 days or partly denervated by spinal root section for up to 63 days; the intramuscular and extramuscular nerves were then examined in the electron microscope in thin sections of tissue fixed conventionally or stained with zinc iodide-osmium tetroxide. Contralateral muscles were also examined as controls. The distribution of nodal sprouts in the nerves of the paralysed or partly denervated muscles was determined by calculating the mean ratios of unmyelinated to myelinated axons in nerve profiles containing different numbers of myelinated axons (intact or degenerating) and comparing these with control ratios. In paralysed muscles there was a significantly higher proportion of nerve profiles containing one or two unmyelinated axons alongside a single myelinated axon. Nerve profiles containing two or more myelinated axons did not show any increase in the proportion of unmyelinated axons. Thus, there is probably nodal sprouting in paralysed muscles which is restricted to the most distal nodes of the intramuscular nerves. In muscles partly denervated for 8 days there were significant increases in the proportion of unmyelinated axons in nerve profiles which had contained up to 5-10 myelinated axons. After 21 days of partial denervation, similar increases may have occurred in the larger intramuscular nerve profiles and after 63 days there were large increases in the proportion of unmyelinated axons in the main intramuscular nerve branches and in the extramuscular nerve. Nodal sprouting in response to partial denervation is therefore localised initially to the smaller, more distal nerve branches; at later times, some sprouts probably grow slowly in a disto-proximal direction along denervated Schwann cell pathways. The existence of nodal sprouts in paralysed muscles and their restricted distribution in paralysed and partly denervated muscles suggest that the nodal sprouting stimulus is produced by the muscle and acts only at distal nodes.
将成年小鼠的右臀大肌用肉毒杆菌毒素使其麻痹长达21天，或通过切断脊神经根使其部分失神经支配长达63天；然后在电子显微镜下检查常规固定或用碘化锌-四氧化锇染色的组织薄片中的肌内和肌外神经。对侧肌肉也作为对照进行检查。通过计算含有不同数量有髓轴突（完整或退变）的神经断面中无髓轴突与有髓轴突的平均比例，并将这些比例与对照比例进行比较，来确定麻痹或部分失神经支配肌肉的神经中结旁芽的分布。在麻痹的肌肉中，含有一个或两个无髓轴突与单个有髓轴突并存的神经断面比例明显更高。含有两个或更多有髓轴突的神经断面中无髓轴突的比例没有增加。因此，麻痹肌肉中可能存在结旁芽生，且仅限于肌内神经的最远端结。在部分失神经支配8天的肌肉中，含有多达5 - 10个有髓轴突的神经断面中无髓轴突的比例显著增加。部分失神经支配21天后，较大的肌内神经断面可能也出现了类似的增加，而在63天后，主要肌内神经分支和肌外神经中无髓轴突的比例大幅增加。因此，对部分失神经支配的反应性结旁芽生最初定位于较小、更远端的神经分支；在后期，一些芽可能沿着失神经的施万细胞途径以远 - 近端方向缓慢生长。麻痹肌肉中结旁芽的存在及其在麻痹和部分失神经支配肌肉中的局限分布表明，结旁芽生刺激是由肌肉产生的，且仅作用于远端结。
