Department of Neuroscience Physiology and Pharmacology (NPP), University College London, London WC1E 6BT, UK.
Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK.
Brain. 2024 Feb 1;147(2):406-413. doi: 10.1093/brain/awad342.
Neurophysiological methods are used widely to gain information about motor neuron excitability and axon conduction in neurodegenerative diseases. The F-wave is a common biomarker used to test motor neuron properties in the diagnosis of neurological diseases. Although the origin of the F-wave is a subject of debate, the most widely accepted mechanism posits that the F-wave is generated by the backfiring of motor neurons stimulated antidromically from the periphery. In this study, we developed an ex vivo mouse sciatic nerve-attached spinal cord preparation with sensory axons severed. In this preparation, stimulation of the whole sciatic nerve or its tibial branch evoked responses with the electrophysiological signatures of F-waves. Manipulations of synaptic transmission by either removal of extracellular calcium or block of post-synaptic glutamate receptors abolished these responses. These results suggest that F-waves are mediated by spinal microcircuits activated by recurrent motor axon collaterals via glutamatergic synapses.
神经生理学方法广泛用于获得神经退行性疾病中运动神经元兴奋性和轴突传导的信息。F 波是一种常用的生物标志物，用于测试神经疾病诊断中的运动神经元特性。尽管 F 波的起源存在争议，但最广泛接受的机制假设 F 波是由从外围逆行刺激的运动神经元反向激发产生的。在这项研究中，我们开发了一种具有切断感觉轴突的离体小鼠坐骨神经附着脊髓制备物。在该制备物中，刺激整个坐骨神经或其胫神经分支会引起具有 F 波特征的电生理反应。通过去除细胞外钙或阻断突触后谷氨酸受体来操纵突触传递会消除这些反应。这些结果表明，F 波是由通过谷氨酸能突触激活的脊髓微电路介导的，这些微电路是由反复的运动轴突侧支激活的。
