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Neuroglia 2018, 1(1), 271-279; https://doi.org/10.3390/neuroglia1010018

Syncytial Isopotentiality: An Electrical Feature of Spinal Cord Astrocyte Networks

1
Department of Spine Surgery, Wuhan First Hospital, Wuhan 430022, China
2
Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
3
Department of Neurology, Wuhan First Hospital, Wuhan 430022, China
*
Author to whom correspondence should be addressed.
Received: 2 August 2018 / Revised: 20 August 2018 / Accepted: 22 August 2018 / Published: 24 August 2018
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Abstract

Due to strong electrical coupling, syncytial isopotentiality emerges as a physiological mechanism that coordinates astrocytes into a highly efficient system in brain homeostasis. Although this electrophysiological phenomenon has now been observed in astrocyte networks established by different astrocyte subtypes, the spinal cord remains a brain region that is still unexplored. In ALDH1L1-eGFP transgenic mice, astrocytes can be visualized by confocal microscopy and the spinal cord astrocytes in grey matter are organized in a distinctive pattern. Namely, each astrocyte resides with more directly coupled neighbors at shorter interastrocytic distances compared to protoplasmic astrocytes in the hippocampal CA1 region. In whole-cell patch clamp recording, the spinal cord grey matter astrocytes exhibit passive K+ conductance and a highly hyperpolarized membrane potential of −80 mV. To answer whether syncytial isopotentiality is a shared feature of astrocyte networks in the spinal cord, the K+ content in a physiological recording solution was substituted by equimolar Na+ for whole-cell recording in spinal cord slices. In uncoupled single astrocytes, this substitution of endogenous K+ with Na+ is known to depolarize astrocytes to around 0 mV as predicted by Goldman–Hodgkin–Katz (GHK) equation. In contrast, the existence of syncytial isopotentiality is indicated by a disobedience of the GHK predication as the recorded astrocyte’s membrane potential remains at a quasi-physiological level that is comparable to its neighbors due to strong electrical coupling. We showed that the strength of syncytial isopotentiality in spinal cord grey matter is significantly stronger than that of astrocyte network in the hippocampal CA1 region. Thus, this study corroborates the notion that syncytial isopotentiality most likely represents a system-wide electrical feature of astrocytic networks throughout the brain. View Full-Text
Keywords: astrocytes; spinal cord; gap junctions; electrical coupling; syncytial isopotentiality astrocytes; spinal cord; gap junctions; electrical coupling; syncytial isopotentiality
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Huang, M.; Du, Y.; Kiyoshi, C.M.; Wu, X.; Askwith, C.C.; McTigue, D.M.; Zhou, M. Syncytial Isopotentiality: An Electrical Feature of Spinal Cord Astrocyte Networks. Neuroglia 2018, 1, 271-279.

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