Gap junction coupling confers isopotentiality on astrocyte syncytium.
Gap junction coupling confers isopotentiality on astrocyte syncytium.
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作者：
Ma B;Buckalew R;Du Y;Kiyoshi CM;Alford CC;Wang W;McTigue DM;Enyeart JJ;Terman D;Zhou M
星形胶质细胞通过间隙连接广泛耦合成合胞体。然而，这个主要大脑网络的基本作用仍然很大程度上未知。使用电生理学和计算建模方法，我们证明，当用还原或不含 K+ 的移液器溶液记录时，海马合胞体中单个星形胶质细胞的膜电位 (VM) 可以很好地维持在准生理水平，而在单个新鲜分离的细胞制剂中，VM 可以将 K+ 平衡电位改变为非生理电压。我们发现，星形胶质细胞的相关合胞体提供了强大的电耦合，以及较小程度的离子耦合，使星形胶质细胞的 VM 达到与其邻居相当的水平。从功能上讲，这最大限度地减少了由于局部细胞外 K+ 水平升高而导致的 VM 去极化，从而保持了高效 K+ 吸收的持续驱动力。因此，间隙连接耦合的作用是在星形胶质细胞网络中实现等电位，从而可以为神经回路的关键功能强有力地维持恒定的细胞外环境。
Astrocytes are extensively coupled through gap junctions into a syncytium. However, the basic role of this major brain network remains largely unknown. Using electrophysiological and computational modeling methods, we demonstrate that the membrane potential (VM) of an individual astrocyte in a hippocampal syncytium, but not in a single, freshly isolated cell preparation, can be well-maintained at quasi-physiological levels when recorded with reduced or K+ free pipette solutions that alter the K+ equilibrium potential to non-physiological voltages. We show that an astrocyte’s associated syncytium provides powerful electrical coupling, together with ionic coupling at a lesser extent, that equalizes the astrocyte’s VM to levels comparable to its neighbors. Functionally, this minimizes VM depolarization attributable to elevated levels of local extracellular K+ and thereby maintains a sustained driving force for highly efficient K+ uptake. Thus, gap junction coupling functions to achieve isopotentiality in astrocytic networks, whereby a constant extracellular environment can be powerfully maintained for crucial functions of neural circuits.