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Glia. 2016 Feb;64(2):214-26. doi: 10.1002/glia.22924. Epub 2015 Oct 5.

Gap junction coupling confers isopotentiality on astrocyte syncytium.

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Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
Mathematical Biosciences Institute, the Ohio State University, Columbus, Ohio, 43210.
Department of Mathematics, the Ohio State University, Columbus, Ohio, 43210.


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.


K+ clearance; coupling coefficient; electrical coupling; membrane potential

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