Wild Brandon M, Morris Renée, Moldovan Mihai, Krarup Christian, Krishnan Arun V, Arnold Ria
School of Medical Science, University of New South Wales.
Department of Clinical Neurophysiology, Rigshospitalet and the Institute of Neuroscience and Pharmacology, University of Copenhagen.
J Vis Exp. 2018 Feb 6(132):56102. doi: 10.3791/56102.
Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques "by threshold tracking" expand upon these measures by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve. The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate and saturation of oxygen in the blood are continuously monitored. Axonal excitability studies are performed using percutaneous stimulation of the ulnar nerve and recording from the hypothenar muscles of the forelimb paw. With correct electrode placement, a clear compound muscle action potential that increases in amplitude with increasing stimulus intensity is recorded. An automated program is then utilized to deliver a series of electrical pulses which generate 5 specific excitability measures in the following sequence: stimulus response behavior, strength duration time constant, threshold electrotonus, current-threshold relationship and the recovery cycle. Data presented here indicate that these measures are repeatable and show similarity between left and right ulnar nerves when assessed on the same day. A limitation of these techniques in this setting is the effect of dose and time under anesthesia. Careful monitoring and recording of these variables should be undertaken for consideration at the time of analysis.
电生理学能够在体内对外周神经功能进行客观评估。传统的神经传导测量指标，如波幅和潜伏期，分别用于检测慢性轴突损失和脱髓鞘。通过阈值跟踪的轴突兴奋性技术扩展了这些测量方法，提供了与离子通道、泵和交换器活性相关的信息，这些与急性功能有关且可能先于退行性事件发生。因此，在神经疾病动物模型中使用轴突兴奋性可能提供一种有用的体内测量方法，以评估新型治疗干预措施。在此，我们描述一种用于大鼠尺神经运动轴突兴奋性技术多种测量的实验装置。动物用异氟烷麻醉，并仔细监测以确保麻醉深度恒定且充足。持续监测体温、呼吸频率、心率和血液中的氧饱和度。轴突兴奋性研究通过经皮刺激尺神经并从前肢爪的小鱼际肌记录来进行。电极放置正确时，可记录到随着刺激强度增加波幅增大的清晰复合肌肉动作电位。然后利用一个自动化程序发送一系列电脉冲，按以下顺序产生5种特定的兴奋性测量指标：刺激反应行为、强度-时间常数、阈下电紧张、电流-阈值关系和恢复周期。此处呈现的数据表明，这些测量指标具有可重复性，并且在同一天评估时，左右尺神经之间表现出相似性。在这种情况下，这些技术的一个局限性是麻醉剂量和时间的影响。在分析时应仔细监测和记录这些变量以供考虑。
