Lebovitz R M
Biophys J. 1970 May;10(5):423-44. doi: 10.1016/S0006-3495(70)86310-X.
Evidence from electron microscopy indicates that the separation between adjacent membranes of the central nervous system (CNS) is less than 500 A and perhaps as small as 100-250 A. The rapid K(+) efflux associated with the neural action potential may therefore be sufficient to affect the local extracellular potassium concentration and, via their partial dependence upon the potassium equilibrium potential, alter the electrical states of nearby neural and glial membranes. This new concept of a transient and local depolarizing "ionic interaction" between active and inactive membranes of the CNS is here examined theoretically and its magnitude calculated as a function of (a) the intermembrane separation, (b) the membranes' electrochemical characteristics, and (c) the rate at which K(+) can diffuse away from the vicinity of the active (neural) membrane. My results indicate that the interaction is in the millivolt range and therefore significant in the modulation of postsynaptic and presynaptic information processing; in particular configurations the postulated interaction alone may be suprathreshold. Membrane noise and local synchrony in groups of neurons may reflect these local, K(+)-mediated interactions. The transient ionic interaction between active neural and nearby glial membrane is also in the millivolt range; however, the relevance of neuroglia to neuronal function is obscure. Certain pathological states, such as seizure and spreading depression, have an obvious phenomenological correspondence to the results presented here and are briefly discussed.
电子显微镜证据表明，中枢神经系统（CNS）相邻膜之间的间距小于500埃，可能小至100 - 250埃。因此，与神经动作电位相关的快速钾离子外流可能足以影响局部细胞外钾离子浓度，并通过它们对钾离子平衡电位的部分依赖性，改变附近神经和胶质细胞膜的电状态。本文从理论上研究了中枢神经系统活动膜和非活动膜之间短暂局部去极化“离子相互作用”这一新概念，并根据（a）膜间距、（b）膜的电化学特性以及（c）钾离子从活动（神经）膜附近扩散离开的速率计算了其大小。我的结果表明，这种相互作用在毫伏范围内，因此在突触后和突触前信息处理的调制中具有重要意义；在特定构型中，仅假定的相互作用可能就高于阈值。神经元群体中的膜噪声和局部同步性可能反映了这些局部的、由钾离子介导的相互作用。活动神经膜与附近胶质细胞膜之间的短暂离子相互作用也在毫伏范围内；然而，神经胶质细胞与神经元功能的相关性尚不清楚。某些病理状态，如癫痫发作和扩散性抑制，与本文给出的结果具有明显的现象学对应关系，并在此进行简要讨论。
