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Microglial NO induces delayed neuronal death following acute injury in the striatum

Authors

  • Akihide Takeuchi,

    1. Department of Immunology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466, Japan,
    2. Division of Gerontology, National Institute for Longevity Sciences, 36-3 Gengo, Morioka-cho, Obu, Aichi 474, Japan,
    3. Laboratory for Genes of Motor Systems, Bio-Mimetic Control Research Program, RIKEN, 2271-130 Anagahora, Shimoshidami, Moriyama-ku, Nagoya, Aichi 463, Japan,
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  • Ken-ichi Isobe,

    1. Department of Immunology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466, Japan,
    2. Division of Gerontology, National Institute for Longevity Sciences, 36-3 Gengo, Morioka-cho, Obu, Aichi 474, Japan,
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  • Osamu Miyaishi,

    1. Division of Gerontology, National Institute for Longevity Sciences, 36-3 Gengo, Morioka-cho, Obu, Aichi 474, Japan,
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  • Makoto Sawada,

    1. Laboratory for Genes of Motor Systems, Bio-Mimetic Control Research Program, RIKEN, 2271-130 Anagahora, Shimoshidami, Moriyama-ku, Nagoya, Aichi 463, Japan,
    2. Division of Pathology and Biochemistry, Institute for Comprehensive Medical Sciences, Fujita Health University, Toyoake, Aichi 470-11, Japan
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  • Zou-Heng Fan,

    1. Department of Immunology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466, Japan,
    2. Laboratory for Genes of Motor Systems, Bio-Mimetic Control Research Program, RIKEN, 2271-130 Anagahora, Shimoshidami, Moriyama-ku, Nagoya, Aichi 463, Japan,
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  • Izumi Nakashima,

    1. Department of Immunology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466, Japan,
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  • Kazutoshi Kiuchi

    1. Laboratory for Genes of Motor Systems, Bio-Mimetic Control Research Program, RIKEN, 2271-130 Anagahora, Shimoshidami, Moriyama-ku, Nagoya, Aichi 463, Japan,
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Correspondence: K. Kiuchi, as above. E-mail: kiuchi@nagoya.riken.go.jp

Abstract

We have established a novel injury model in the central nervous system by a stereotaxic injection of ethanol into rat striatum to induce necrosis. With this model, we clarify a function of inducible nitric oxide synthase (iNOS) in a healing mechanism around a necrotic lesion. A semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that the iNOS mRNA arose at 6 h, peaked at 24 h, and declined to a lower level 48 h after an intrastriatal 5-μL ethanol injection. From in situ hybridization, this iNOS mRNA was expressed in the area surrounding the injury. By immunohistochemistry, mononuclear cells at this boundary area of necrosis were stained with anti-iNOS antibody on the first day after the injury. These cells turned out to be reactive microglia from the positive staining of GSA-I-B4, ED-1 and OX-42. Haematoxylin-eosin (HE) staining showed that neurons in this boundary area gradually disappear up to 5 days after the injury with an increment of microglial cells, and this area became cavernous. Nuclei of neurons in this area were stained positive by the terminal deoxynucleotidyl-transferase-mediated dUTP-biotin nick end-labelling (TUNEL) assay on the first day after the injury. These TUNEL-positive neurons gradually disappeared toward the third day, while microglial cells increased. L-Ng-nitro-arginine methylester (L-NAME), a competitive NOS inhibitor, administration diminished the elimination of neurons by microglia in this boundary area surrounding necrosis. Microglial NO may act as a neurotoxic agent to eliminate damaged neurons near the necrosis in the form of delayed neuronal death, and may reintegrate the neuronal circuits with functionally intact neurons.

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