Sernagor E, Yarom Y, Werman R
Proc Natl Acad Sci U S A. 1986 Oct;83(20):7966-70. doi: 10.1073/pnas.83.20.7966.
Ten days after extradural axotomy, partial spikes are found in greater than 20% of cat L7 motoneurons, while 15-21 days after axotomy the incidence increases to 60%. These responses are produced in excitable (hot) spots in the dendrites by synaptic excitation. Intracellular injection of QX-314, a lidocaine derivative and effective blocker of Na+ channels from within neurons, results in elimination of partial spikes before blocking somadendritic spikes. The action of QX-314 does not depend on changes in passive membrane properties or on changes in synaptic properties. Injections of Cs+ and Cl- ions rule out any major role for calcium, potassium, or chloride currents in the production of partial spikes. The partial spikes represent an unusual Na+-dependent dendritic phenomenon induced by axotomy when carried out relatively near the soma. It is reasonable to postulate that the partial spikes result from a higher concentration of Na+ channels in the dendrites. This may be the consequence of a high rate of production of Na+-channel proteins that are intended for the cut end of the axon; alternatively, they may result from the reflection from the cut end of such proteins produced at either a normal or an increased rate. These aberrant channels are inserted into somatic and dendritic membranes in higher concentrations than normal and, as well as producing local dendritic regions of low safety factor responsible for the partial spikes, also produce somadendritic spikes of unusually fast rise time and lower than usual threshold, which are relatively resistant to QX-314.
硬膜外轴突切断术后10天，超过20%的猫L7运动神经元出现部分棘波，而轴突切断术后15 - 21天，这一发生率增至60%。这些反应是由突触兴奋在树突中的可兴奋（热点）区域产生的。细胞内注射QX - 314（一种利多卡因衍生物，是神经元内有效的Na⁺通道阻滞剂），会在阻断胞体树突棘波之前消除部分棘波。QX - 314的作用不依赖于被动膜特性的改变或突触特性的改变。注射Cs⁺和Cl⁻离子排除了钙、钾或氯电流在部分棘波产生过程中的任何主要作用。部分棘波代表了在相对靠近胞体处进行轴突切断时由轴突切断诱导的一种不寻常的依赖Na⁺的树突现象。推测部分棘波是由树突中较高浓度的Na⁺通道所致是合理的。这可能是由于打算用于轴突切断端的Na⁺通道蛋白产生速率较高的结果；或者，它们可能是由正常或增加速率产生的此类蛋白从切断端反射而来。这些异常通道以高于正常的浓度插入到胞体和树突膜中，并且除了产生负责部分棘波的低安全系数的局部树突区域外，还产生上升时间异常快且阈值低于正常的胞体树突棘波，这些棘波对QX - 314相对耐药。
