Wood M R, Cohen M J
J Neurocytol. 1981 Feb;10(1):57-79. doi: 10.1007/BF01181745.
We have examined axonal growth and synaptic regeneration in identified giant neurons of the transected lamprey spinal cord using intracellular injection of horseradish peroxidase. Wholemounts together with serial section light and electron microscopy, show that axons from identified Müller and Mauthner reticulospinal neurons grow across the lesion and regenerate new synaptic contacts. Relatively normal swimming returns in these animals by 3-4 weeks after spinal transection. This occurs despite the formation of regenerated synapses in regions of the cord that are not usually occupied by these neurons. The regenerating axons branch profusely in contrast to their unbranched state in the normal animal. In addition to showing the two synaptic configuration found normally, synapses may be formed by slender sprouts from the growing giant axon. These 'sprout' type synaptic contacts appear unique to the regenerating neuron. Only regenerated chemical synapses were seen; the morphologically mixed chemical and electrical (gap junction) synaptic complex common in the normal animal was not observed at regenerated synapses. The site of spinal transection in the functionally recovered animal shows an increase in the number of ependymal and glial cells. Ependymal-like cells appear in regions away from the central canal. The expanded ependymal and glial processes covering the peripheral surface of the injured cord become convoluted, in contrast to their normal smooth configuration. There is no collagen within the cord at the site of transection but a considerable deposition is seen external to the cord surface. Axonal growth across a spinal lesion and subsequent synaptic regeneration can be examined in single identifiable giant interneurons in the spinal cord of the larval lamprey. This preparation may be used as an assay to investigate factors that could contribute to functional recovery following central nervous system injury in the higher vertebrates.
我们利用辣根过氧化物酶的细胞内注射，研究了经横断的七鳃鳗脊髓中特定巨型神经元的轴突生长和突触再生。整体标本连同连续切片的光镜和电镜观察表明，已识别的米勒氏神经元和莫特纳尔氏网状脊髓神经元的轴突穿过损伤部位并再生出新的突触联系。脊髓横断后3至4周，这些动物的游泳功能相对正常地恢复。尽管在脊髓中通常并非这些神经元占据的区域形成了再生突触，但仍出现了这种情况。与正常动物中未分支的状态相比，再生轴突大量分支。除了呈现正常情况下发现的两种突触结构外，生长中的巨型轴突的细长芽体也可能形成突触。这些“芽体”型突触联系似乎是再生神经元所特有的。仅观察到再生的化学突触；在再生突触处未观察到正常动物中常见的形态学上混合的化学和电（缝隙连接）突触复合体。功能恢复的动物脊髓横断部位的室管膜细胞和神经胶质细胞数量增加。室管膜样细胞出现在远离中央管的区域。覆盖受损脊髓外周表面的扩张的室管膜和神经胶质突起变得卷曲，与其正常的光滑形态形成对比。横断部位的脊髓内没有胶原蛋白，但在脊髓表面外部可见大量沉积。在幼虫七鳃鳗的脊髓中，可以在单个可识别的巨型中间神经元中研究轴突跨脊髓损伤的生长及随后的突触再生。该制备方法可作为一种检测方法，用于研究可能有助于高等脊椎动物中枢神经系统损伤后功能恢复的因素。
