Ma Baofeng, Buckalew Richard, Du Yixing, Kiyoshi Conrad M, Alford Catherine C, Wang Wei, McTigue Dana M, Enyeart John J, Terman David, Zhou Min
Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
Mathematical Biosciences Institute, the Ohio State University, Columbus, Ohio, 43210.
Glia. 2016 Feb;64(2):214-26. doi: 10.1002/glia.22924. Epub 2015 Oct 5.
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.
星形胶质细胞通过缝隙连接广泛连接形成一个合胞体。然而，这个主要脑网络的基本作用在很大程度上仍然未知。使用电生理和计算建模方法，我们证明，当用改变钾离子平衡电位至非生理电压的低浓度或无钾移液管溶液记录时，海马合胞体中单个星形胶质细胞的膜电位（VM）能够维持在准生理水平，而在新鲜分离的单个细胞标本中则不能。我们表明，星形胶质细胞相关的合胞体提供了强大的电耦合，以及程度较小的离子耦合，使星形胶质细胞的VM与其相邻细胞的水平相当。在功能上，这将由于局部细胞外钾离子水平升高引起的VM去极化降至最低，从而维持高效钾离子摄取的持续驱动力。因此，缝隙连接耦合的作用是在星形胶质细胞网络中实现等电位，从而可以有力地维持恒定的细胞外环境以支持神经回路的关键功能。
