title: Electrophysiological behavior of neonatal astrocytes in hippocampal stratum radiatum.
abstract: BACKGROUND
  Neonatal astrocytes are diverse in origin, and undergo dramatic change in gene expression, morphological differentiation and  syncytial networking throughout development. Neonatal astrocytes also play multifaceted roles in neuronal circuitry establishment. However, the extent to which neonatal astrocytes differ from their counterparts in the adult brain remains unknown.
  
  
  RESULTS
  Based on ALDH1L1-eGFP expression or sulforhodamine 101 staining, neonatal astrocytes at postnatal day 1-3 can be reliably identified in hippocampal stratum radiatum. They exhibit a more negative resting membrane potential (V M), -85 mV, than mature astrocytes, -80 mV and a variably rectifying whole-cell current profile due to complex expression of voltage-gated outward transient K(+) (IKa), delayed rectifying K(+) (IKd) and inward K(+) (IKin) conductances. Differing from NG2 glia, depolarization-induced inward Na(+) currents (INa) could not be detected in neonatal astrocytes. A quasi-physiological V M of -69 mV was retained when inwardly rectifying Kir4.1 was inhibited by 100 μM Ba(2+) in both wild type and TWIK-1/TREK-1 double gene knockout astrocytes, indicating expression of additional leak K(+) channels yet unknown. In dual patch recording, electrical coupling was detected in 74 % (14/19 pairs) of neonatal astrocytes with largely variable coupling coefficients. The increasing gap junction coupling progressively masked the rectifying K(+) conductances to account for an increasing number of linear voltage-to-current relationship passive astrocytes (PAs). Gap junction inhibition, by 100 μM meclofenamic acid, substantially reduced membrane conductance and converted all the neonatal PAs to variably rectifying astrocytes. The low density expression of leak K(+) conductance in neonatal astrocytes corresponded  to a ~50 % less K(+) uptake capacity compared to adult astrocytes.
  
  
  CONCLUSIONS
  Neonatal astrocytes predominantly express a variety of rectifying K(+) conductances, form discrete cell-to-cell gap junction coupling and are deficient in K(+) homeostatic capacity.
authors.affiliation: Department of Neurology, Shanghai 10th Hospital of Tongji University, School of Medicine, 301 Yan Chang Zhong Road, Shanghai, 200072, China.|Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Shiying
authors.initials: S
authors.lastname: Zhong
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Yixing
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Conrad M
authors.initials: CM
authors.lastname: Kiyoshi
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Ma
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Alford
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Neurology, Shanghai 10th Hospital of Tongji University, School of Medicine, 301 Yan Chang Zhong Road, Shanghai, 200072, China. liuxy@tongji.edu.cn.
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Neuroscience, Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA. zhou.787@osu.edu.
authors.forename: Min
authors.identifier: http://orcid.org/0000-0002-4425-5326
authors.initials: M
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001464:Barium / Q000378:metabolism; D055724:Electrophysiological Phenomena; D017629:Gap Junctions / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D015640:Ion Channel Gating; D007700:Kinetics; D008810:Mice, Inbred C57BL; D010641:Phenotype; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism
chemical_list: D024661:Potassium Channels, Inwardly Rectifying; D001464:Barium
keywords: Astrocytes; Gap junctions; Hippocampus; K+ conductance; K+ homeostasis