title: Gap junction coupling confers isopotentiality on astrocyte syncytium.
abstract: 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.
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Ma
authors.affiliation: Mathematical Biosciences Institute, the Ohio State University, Columbus, Ohio, 43210.
authors.forename: Richard
authors.initials: R
authors.lastname: Buckalew
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Yixing
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Conrad M
authors.initials: CM
authors.lastname: Kiyoshi
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Alford
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Dana M
authors.initials: DM
authors.lastname: McTigue
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: John J
authors.initials: JJ
authors.lastname: Enyeart
authors.affiliation: Department of Mathematics, the Ohio State University, Columbus, Ohio, 43210.
authors.forename: David
authors.initials: D
authors.lastname: Terman
authors.affiliation: Department of Neuroscience, the Ohio State University Wexner Medical Center, Columbus, Ohio, 43210.
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000502:physiology*; D002414:Cations, Monovalent / Q000378:metabolism; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006624:Hippocampus / Q000502:physiology; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D046509:Tissue Culture Techniques
chemical_list: D002414:Cations, Monovalent; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D011188:Potassium
keywords: K+ clearance; coupling coefficient; electrical coupling; membrane potential