纳米级髓鞘下间隙介导高效的K$^+$摄取并塑造结性动作电位

中文摘要 AI 辅助

髓鞘膜与轴突紧密相连，形成一条电学通路，使动作电位能够从郎飞结到郎飞结快速跳跃式传导。在髓鞘下方、紧邻郎飞结处，存在电压门控钾（K$^+$）通道，但它们在传导中的基本作用仍知之甚少。受生物学数据约束，我们开发了一个郎飞结的有限元模型，该模型包含一个将少突胶质细胞胞质与轴突周围间隙分隔开的轴突旁膜，并求解了控制纳米尺度电扩散和电压分布的全耦合物理方程组。值得注意的是，我们发现结性动作电位在内部轴突旁髓鞘膜处发生反转。超极化驱动的髓鞘Kir4.1通道开放产生瞬时、强大的K$^+$预缓冲作用，钳制轴突周围K$^+$浓度，从而实现高频动作电位的产生。总之，这些发现表明轴突周围与郎飞结之间维持着一个电反馈回路，并提示了结旁K$^+$通道定位的关键进化优势。

英文摘要

Myelin membranes are tightly connected to the axon, forming an electrical route for rapid saltatory conduction of action potentials from node to node. Beneath the myelin, adjacent to the node, lie voltage-gated potassium (K$^+$) channels, whose fundamental role in conduction remains poorly understood. Constrained by biological data, we developed a finite element model of a node of Ranvier encompassing an adaxonal membrane separating oligodendrocyte cytoplasm from the periaxonal space, and solved the full coupled set of physical equations governing electrodiffusion and voltage profiles at the nanoscale. Remarkably, we find that nodal action potentials invert at the inner adaxonal myelin membrane. The hyperpolarization-driven opening of myelinic Kir4.1 channels produces an instantaneous, powerful K$^+$ prebuffering, clamping the periaxonal K$^+$ concentration and enabling high-frequency action potential generation. Together, these findings indicate that the periaxon maintains an electrical feedback loop with the node, and suggest a key evolutionary advantage of juxtaparanodal K$^+$ channel positioning.

发表机构

• Utrecht University（乌得勒支大学）
• Netherlands Institute for Neuroscience (NIN), an Institute of the Royal Netherlands Academy of Arts and Sciences (KNAW)（荷兰神经科学研究所（NIN），荷兰皇家艺术与科学院（KNAW）下属研究所）

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