中国神经再生研究(英文版) ›› 2022, Vol. 17 ›› Issue (10): 2272-2277.doi: 10.4103/1673-5374.335828

• 原著:脊髓损伤修复保护与再生 • 上一篇    下一篇

七鳃鳗脊髓病变部位再生轴突的生理学功能特性

  

  • 出版日期:2022-10-15 发布日期:2022-03-16

The functional properties of synapses made by regenerated axons across spinal cord lesion sites in lamprey

David Parker*   

  1. Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge, UK
  • Online:2022-10-15 Published:2022-03-16
  • Contact: David Parker, PhD, djp27@cam.ac.uk.

摘要:

目前虽然有大量研究涉及再生轴突在整个脊髓病变部位的解剖学特性,但对病变部位再生轴突与非病变部位轴突的生理学功能特性对比研究尚几乎未见。由此,实验建立了七鳃鳗脊髓损伤模型,比较脊髓损伤后再生轴突和未受损伤的轴突的生理学功能特性。结果发现,来自病变部位以下的侧柱网状脊髓轴突的突触输入在其振幅和活动依赖的可塑性方面与未受损伤的轴突相匹配。然而,尽管产生了相同的输出,但释放特性却不同。相反,病变部位以上的轴突建立的连接与未受损伤的脊髓中的连接不同,因为它们显示了从相同的初始兴奋性突触后电位振幅发展而来的促进作用,因此在功能上会更强。说明七鳃鳗脊髓损伤病变部位下方再生的突触显示了其释放特性的变化,这些变化对病变后运动功能的成功恢复非常重要。此外,病变部位以上的突触显示出的功能变化可能是对病变部位以下突触输入减少的一种补偿。

https://orcid.org/0000-0002-5345-348X (David Parker)

Abstract: While the anatomical properties of regenerated axons across spinal cord lesion sites have been studied extensively, little is known of how the functional properties of regenerated synapses compared to those in unlesioned animals. This study aims to compare the properties of synapses made by regenerated axons with unlesioned axons using the lamprey, a model system for spinal injury research, in which functional locomotor recovery after spinal cord lesions is associated with axonal regeneration across the lesion site. Regenerated synapses below the lesion site did not differ from synapses from unlesioned axons with respect to the amplitude and duration of single excitatory postsynaptic potentials. They also showed the same activity-dependent depression over spike trains. However, regenerated synapses did differ from unlesioned synapses as the estimated number of synaptic vesicles was greater and there was evidence for increased postsynaptic quantal amplitude. For axons above the lesion site, the amplitude and duration of single synaptic inputs also did not differ significantly from unlesioned animals. However, in this case, there was evidence of a reduction in release probability and inputs facilitated rather than depressed over spike trains. Synaptic inputs from single regenerated axons below the lesion site thus do not increase in amplitude to compensate for the reduced number of descending axons after functional recovery. However, the postsynaptic input was maintained at the unlesioned level using different synaptic properties. Conversely, the facilitation from the same initial amplitude above the lesion site made the synaptic input over spike trains functionally stronger. This may help to increase propriospinal activity across the lesion site to compensate for the lesion-induced reduction in supraspinal inputs. The animal experiments were approved by the Animal Ethics Committee of Cambridge University.

Key words: electrophysiology, lamprey, plasticity, regeneration, reticulospinal axon, spinal cord, spinal injury, synapse