Laboratory of Molecular Neurobiology, Southern Federal University, 194/1 Stachky ave., Rostov-on-Don 344090, Russia.
Laboratory of Molecular Neurobiology, Southern Federal University, 194/1 Stachky ave., Rostov-on-Don 344090, Russia.
Mol Cell Neurosci. 2020 Sep;107:103534. doi: 10.1016/j.mcn.2020.103534. Epub 2020 Jul 24.
Neurotrauma is among main causes of human disability and death. We studied effects of axotomy on ultrastructure and neuronal activity of a simple model object - an isolated crayfish stretch receptor that consists of single mechanoreceptor neurons (MRN) enwrapped by multilayer glial envelope. After isolation, MRN regularly fired until spontaneous activity cessation. Axotomy did not change significantly MRN spike amplitude and firing rate. However, the duration of neuron activity from MRN isolation to its spontaneous cessation decreased in axotomized MRN relative to intact neuron. [Ca] in MRN axon and soma increased 3-10 min after axotomy. Ca entry through ion channels in the axolemma accelerated axotomy-stimulated firing cessation. MRN incubation with Caionophore ionomycin accelerated MRN inactivation, whereas Ca-channel blocker Cd prolonged firing. Activity duration of either intact, or axotomized MRN did not change in the presence of ryanodine or dantrolene, inhibitors of ryanodin-sensitive Ca channels in endoplasmic reticulum. Thapsigargin, inhibitor of endoplasmic reticulum Ca-ATPase, or its activator ochratoxin were ineffective. Ultrastructural study showed that the defect in the axon transected by thin scissors is sealed by fused axolemma, glial and collagen layers. Only the 30-50 μm long segment completely lost microtubules and contained swelled mitochondria. The microtubular bundle remained undamaged at 300 μm away from the axotomy site. However, mitochondria within the 200-300 μm segment were strongly condensed and lost matrix and cristae. Glial and collagen layers exhibited greater damage. Swelling and edema of glial layers, collagen disorganization and rupture occurred within this segment. Thus, axotomy stronger damages glia/collagen envelope, axonal microtubules and mitochondria.
神经创伤是人类残疾和死亡的主要原因之一。我们研究了轴突切断对简单模型对象——孤立的螯虾伸展感受器的超微结构和神经元活动的影响。伸展感受器由单个机械感受器神经元（MRN）组成，被多层神经胶质包裹。分离后，MRN 会有规律地放电，直到自发活动停止。轴突切断并没有显著改变 MRN 尖峰的幅度和放电率。然而，与完整神经元相比，MRN 的活动持续时间从 MRN 分离到自发停止的时间缩短了。轴突切断后 3-10 分钟，MRN 轴突和胞体中的 [Ca]增加。质膜中的离子通道中的 Ca 内流加速了轴突切断刺激的放电停止。MRN 用 Ca 载体离子霉素孵育加速了 MRN 的失活，而 Ca 通道阻滞剂 Cd 延长了放电。在存在肌醇 1,4,5-三磷酸受体（ryanodine 敏感 Ca 通道）抑制剂ryanodine 或 dantrolene 的情况下，无论是完整的还是轴突切断的 MRN 的活动持续时间都没有改变。内质网 Ca-ATP 酶抑制剂 thapsigargin 或其激活剂 ochratoxin 无效。超微结构研究表明，用薄剪刀切断的轴突的缺陷被融合的轴突膜、神经胶质和胶原层封闭。只有 30-50 μm 长的轴突段完全失去微管，含有肿胀的线粒体。在距轴突切断部位 300 μm 处，微管束仍未受损。然而，在 200-300 μm 段内的线粒体强烈浓缩，失去基质和嵴。神经胶质和胶原层显示出更大的损伤。在该段内，神经胶质层肿胀和水肿、胶原解体和破裂。因此，轴突切断对神经胶质/胶原包膜、轴突微管和线粒体的损伤更大。
