Expression of Kir2.1 Channels in Astrocytes Under Pathophysiological Conditions

  • Kang, Shin Jung (Department of Molecular Biology, Sejong University) ;
  • Cho, Sang-hee (Department of Neurology, Pohang e-Hospital, Dong-sin Medical Corporation) ;
  • Park, Kyungjoon (Department of Biology and Department of Life and Nanopharmaceutical Sciences, Kyunghee University) ;
  • Yi, Jihyun (Department of Biology and Department of Life and Nanopharmaceutical Sciences, Kyunghee University) ;
  • Yoo, Soon Ji (Department of Biology and Department of Life and Nanopharmaceutical Sciences, Kyunghee University) ;
  • Shin, Ki Soon (Department of Biology and Department of Life and Nanopharmaceutical Sciences, Kyunghee University)
  • Received : 2007.10.24
  • Accepted : 2007.10.30
  • Published : 2008.02.29

Abstract

Astrocyte ion channels participate in ionic homeostasis in the brain. Inward rectifying potassium channels (Kir channels) in astrocytes have been particularly implicated in $K^+$ homeostasis because of their high open probability at resting potential and their increased conductance at high concentrations of extracellular $K^+$. We examined the expression of the Kir2.1 subunit, one of the Kir channel subunits, in the mouse brain by immunohistochemistry. Kir2.1 channels were widely distributed throughout the brain, with high expression in the olfactory bulb and the cerebellum. Interestingly, they were abundantly expressed in astrocytes of the olfactory bulb, while astrocytes in other brain regions including the hippocampus did not show any detectable expression. However, Kir2.1 channel-expressing cells were dramatically increased in the hippocampus by kainic acid-induced seizure and the cells were glial fibrillary acidic protein (GFAP)-positive, which confirms that astrocytes in the hippocampus express Kir2.1 channels under pathological conditions. Our results imply that Kir2.1 channels in astrocyte may be involved in buffering $K^+$ against accumulated extracellular $K^+$ caused by neuronal hyperexcitability under phathophysiological conditions.

Keywords

Astrocytes;Hippocampus;$K^+$ Homeostasis;Kainic Acid-induced Seizures;Kir2.1;Olfactory Bulb

Acknowledgement

Supported by : Kyung Hee University

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