McKerracher L, Vidal-Sanz M, Essagian C, Aguayo A J
Center for Research in Neuroscience, Montreal General Hospital Research Institute, Quebec, Canada.
J Neurosci. 1990 Aug;10(8):2834-41. doi: 10.1523/JNEUROSCI.10-08-02834.1990.
To investigate cellular responses of injured mammalian CNS neurons, we examined the slow transport of cytoskeletal proteins in rat retinal ganglion cell (RGC) axons within the ocular stump of optic nerves that were crushed intracranially. RGC proteins were labeled by an intravitreal injection of 35S-methionine, and optic nerves were examined by SDS PAGE at different times after injury. In one group of rats, the RGC proteins were labeled 1 week after crushing. From 14 to 67 d after axotomy, the labeling of tubulin and neurofilaments was reduced in relation to other labeled proteins and to the labeling of tubulin and neurofilaments in the intact optic nerve of controls. To determine whether this reduction in labeling was due to an alteration in axonal transport after axotomy, we prelabeled RGC proteins 1 week before crushing. In such experiments, the rate of slow axonal transport of tubulin and neurofilaments decreased approximately 10-fold from 6 to 60 d after injury. Our results cannot be due only to the retrograde degeneration of RGCs and injured axons caused by axotomy in the optic nerve, because fast axonal protein transport and the fluorescent labeling of many axons were preserved in the ocular stumps of these optic nerves. This selective failure of the slow axonal transport of tubulin and neurofilaments may affect the renewal of the cytoskeleton and contribute to the gradual degeneration of RGCs that is observed after axotomy. The alterations in slow transport we document here differ from the enhanced rates we previously reported when injured RGC axons regenerated along peripheral nerve segments grafted to the ocular stump of transected optic nerves (McKerracher et al., 1990).
为了研究受损哺乳动物中枢神经系统神经元的细胞反应，我们检测了大鼠视网膜神经节细胞（RGC）轴突在颅内被挤压的视神经眼内残端中细胞骨架蛋白的慢速运输。通过玻璃体内注射35S-甲硫氨酸标记RGC蛋白，并在损伤后的不同时间通过SDS-PAGE检测视神经。在一组大鼠中，挤压后1周标记RGC蛋白。在轴突切断后14至67天，与其他标记蛋白以及对照组完整视神经中的微管蛋白和神经丝标记相比，微管蛋白和神经丝的标记减少。为了确定这种标记减少是否是由于轴突切断后轴突运输的改变，我们在挤压前1周预标记RGC蛋白。在这些实验中，微管蛋白和神经丝的慢速轴突运输速率在损伤后6至60天下降了约10倍。我们的结果不能仅仅归因于视神经轴突切断引起的RGC和受损轴突的逆行性变性，因为这些视神经的眼内残端中快速轴突蛋白运输和许多轴突的荧光标记得以保留。微管蛋白和神经丝的慢速轴突运输的这种选择性失败可能会影响细胞骨架的更新，并导致轴突切断后观察到的RGC逐渐变性。我们在此记录的慢速运输变化与我们之前报道的受损RGC轴突沿移植到横断视神经眼内残端的外周神经节段再生时运输速率增加的情况不同（McKerracher等人，1990）。
