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The Journal of Neuroscience, February 7, 2007, 27(6):1445-1455; doi:10.1523/JNEUROSCI.4694-06.2007

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Neurobiology of Disease
Roles of Volume-Sensitive Chloride Channel in Excitotoxic Neuronal Injury

Hana Inoue and Yasunobu Okada

Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan

Correspondence should be addressed to Yasunobu Okada at the above address. Email: okada{at}nips.ac.jp

Excitotoxicity is associated with stroke, brain trauma, and a number of neurodegenerative disorders. In the brain, during excitotoxic insults, neurons undergo rapid swelling in both the soma and dendrites. Focal swellings along the dendrites called varicosities are considered to be a hallmark of acute excitotoxic neuronal injury. However, it is not clear what pathway is involved in the neuronal anion flux that leads to the formation and resolution of excitotoxic varicosities. Here, we assessed the roles of the volume-sensitive outwardly rectifying (VSOR) Cl^– channel in excitotoxic responses in mouse cortical neurons. Whole-cell patch-clamp recordings revealed that the VSOR Cl^– channel in cultured neurons was activated by NMDA exposure. Moreover, robust expression of this channel on varicosities was confirmed by on-cell and nystatin-perforated vesicle patch techniques. VSOR channel blockers, but not blockers of GABA_A receptors and Cl^– transporters, abolished not only varicosity resolution after sublethal excitotoxic stimulation but also necrotic death after sustained varicosity formation induced by prolonged NMDA exposure in cortical neurons. The present slice-patch experiments demonstrated, for the first time, expression of the VSOR Cl^– channels in somatosensory pyramidal neurons. NMDA-induced necrotic neuronal death in slice preparations was largely suppressed by a blocker of the VSOR Cl^– channel but not of the GABA_A receptor. These results indicate that VSOR Cl^– channels exert dual, reciprocal actions on neuronal excitotoxicity by serving as major anionic pathways both for varicosity recovery after washout of an excitotoxic stimulant and for persistent varicosity formation under prolonged excitotoxic insults leading to necrosis in cortical neurons.

Key words: anion channel; cortical neuron; excitotoxicity; necrosis; varicosity; volume regulation

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Received Oct. 19, 2005; revised Dec. 19, 2006; accepted Dec. 24, 2006.

Correspondence should be addressed to Yasunobu Okada at the above address. Email: okada{at}nips.ac.jp

This article has been cited by other articles:

				Y. Okada, K. Sato, and T. Numata Pathophysiology and puzzles of the volume-sensitive outwardly rectifying anion channel J. Physiol., May 15, 2009; 587(10): 2141 - 2149. [Abstract] [Full Text] [PDF]

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