Centre for Neuroscience, Surgery and Trauma, Blizard Institute, QMUL 4 Newark Street Whitechapel, London, E1 2AT, UK.
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
Sci Rep. 2021 Oct 15;11(1):20528. doi: 10.1038/s41598-021-00084-1.
Normal optic nerve axons exhibit a temperature dependence, previously explained by a membrane potential hyperpolarization on warming. We now report that near infra-red laser light, delivered via a fibre optic light guide, also affects axonal membrane potential and threshold, at least partly through a photo-thermal effect. Application of light to optic nerve, at the recording site, gave rise to a local membrane potential hyperpolarization over a period of about a minute, and increased the size of the depolarizing after potential. Application near the site of electrical stimulation reversibly raised current-threshold, and the change in threshold recorded over minutes of irradiation was significantly increased by the application of the I blocker, ZD7288 (50 µM), indicating I limits the hyperpolarizing effect of light. Light application also had fast effects on nerve behaviour, increasing threshold without appreciable delay (within seconds), probably by a mechanism independent of kinetically fast K channels and Na channel inactivation, and hypothesized to be caused by reversible changes in myelin function.
正常的视神经轴突表现出温度依赖性，这一现象以前可以用膜电位的超极化来解释。我们现在报告说，近红外激光通过光纤光导传输，也会影响轴突的膜电位和阈值，至少部分是通过光热效应。在记录部位将光施加到视神经上，会在大约一分钟的时间内引起局部膜电位超极化，并增加去极化后电位的幅度。在电刺激部位附近施加光会可逆地增加电流阈值，并且在辐照几分钟内记录的阈值变化通过应用 I 型阻断剂 ZD7288（50μM）显著增加，表明 I 限制了光的超极化作用。光的施加也对神经行为产生了快速的影响，没有明显的延迟（在几秒钟内）就增加了阈值，这可能是通过一种独立于动力学快速 K 通道和 Na 通道失活的机制，并且假设是由髓鞘功能的可逆变化引起的。
