The effect of axotomy on firing and ultrastructure of the crayfish mechanoreceptor neurons and satellite glial cells

• Published in: Molecular and cellular neuroscience 2020-09, Vol.107, p.103534-103534, Article 103534
• Main Authors: Rudkovskii, M.V., Fedorenko, A.G., Khaitin, A.M., Pitinova, M.A., Uzdensky, A.B.
• Format: Article
• Language: English
• Subjects: Axotomy; Ca2; Glia; Microtubules; Mitochondria; Neuron activity
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2020.103534

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. [Ca2+] in MRN axon and soma increased 3–10 min after axotomy. Ca2+ entry through ion channels in the axolemma accelerated axotomy-stimulated firing cessation. MRN incubation with Ca2+ionophore ionomycin accelerated MRN inactivation, whereas Ca2+-channel blocker Cd2+ prolonged firing. Activity duration of either intact, or axotomized MRN did not change in the presence of ryanodine or dantrolene, inhibitors of ryanodin-sensitive Ca2+ channels in endoplasmic reticulum. Thapsigargin, inhibitor of endoplasmic reticulum Ca2+-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. •Axotomy of crayfish mechanoreceptor neuron (MRN) was studied.•Axotomy shortened MRN firing duration due to Ca2+ penetration through ion channels.•Glial and collagen layers assist axon sealing after axotomy.•Axotomy caused loss of microtubules and damaged mitochondria in 30 μm axon fragment.•Axotomy induced swelling and edema of glia, collagen disorganization and rupture.