Spira M E, Yarom Y, Zeldes D
J Exp Biol. 1984 Sep;112:179-97. doi: 10.1242/jeb.112.1.179.
Neuronal interactions mediated by alteration of the extracellular K+ concentration [K+]o occur between populations as well as among single neurones in very restricted regions. The interactions mediated by K+ ions may range from low efficacy ones (in which the effects of increased [K+]o around the non-active cells can be recorded only after massive activity of a large population of neurones) to very effective interactions (in which a single action potential in a neurone is sufficient to produce a depolarization of several mV in a second one). Such efficient K+-mediated interactions cannot be unequivocally distinguished by shape, amplitude or time course from postsynaptic responses induced by chemical or electrotonic synapses. We review here experiments which demonstrate various levels of interactions mediated by changes in potassium ion concentration. The giant axons (Gax) and non-giant axons from the central nervous system of the cockroach Periplaneta americana were used. The types of interactions discussed are: pathological interactions among populations of neurones induced by the convulsant drug picrotoxin; restricted and limited interactions which are the consequence of the combination of the special geometry of Gaxs and increases in extracellular K+; and finally, local and efficient interactions among Gaxs which are postulated to be mediated by K+ ions. The experiments described in this review, as well as others, demonstrate that the extracellular spaces in the CNS serve as predetermined pathways for K+-mediated neuronal communication. When the extracellular space between two adjacent neurones is very small, the K+-mediated interaction may resemble the PSPs of chemical or electrotonic synapses. It is possible that because of this resemblance, other K+-mediated interactions in the CNS have not been identified as such.
由细胞外钾离子浓度[K⁺]ₒ改变介导的神经元相互作用，既发生在不同神经元群体之间，也发生在非常局限区域内的单个神经元之间。由钾离子介导的相互作用范围很广，从低效相互作用（即只有在大量神经元群体产生大量活动后，才能记录到非活动细胞周围[K⁺]ₒ升高的影响）到高效相互作用（即一个神经元的单个动作电位足以使另一个神经元产生几毫伏的去极化）。这种高效的钾离子介导的相互作用，在形状、幅度或时间进程上，无法与化学或电紧张性突触诱导的突触后反应明确区分。我们在此回顾一些实验，这些实验证明了由钾离子浓度变化介导的不同水平的相互作用。实验使用了美洲大蠊中枢神经系统中的巨轴突（Gax）和非巨轴突。所讨论的相互作用类型包括：惊厥药物印防己毒素诱导的神经元群体之间的病理性相互作用；由Gax的特殊几何结构与细胞外钾离子增加共同作用导致的局限和有限的相互作用；以及最后推测为由钾离子介导的Gax之间的局部和高效相互作用。本综述中描述的实验以及其他实验表明，中枢神经系统中的细胞外空间充当了钾离子介导的神经元通讯的预定通路。当两个相邻神经元之间的细胞外空间非常小时，钾离子介导的相互作用可能类似于化学或电紧张性突触的突触后电位。可能正是由于这种相似性，中枢神经系统中其他钾离子介导的相互作用尚未被识别出来。
