Branchiogenic motoneurons innervating facial, masticatory, and esophageal muscles show aberrant distribution in the reeler-phenotype mutant rat, Shaking Rat Kawasaki

Authors

  • Tomiyoshi Setsu,

    1. Department of Anatomy, Kobe University School of Medicine, Kobe 650-0017, Japan
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  • Yayoi Ikeda,

    1. Department of Anatomy and Embryology, Tokyo Metropolitan Institute for Neuroscience, Fuchu 183-8526, Japan
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  • Peter L. Woodhams,

    1. Division of Neurobiology, National Institute for Medical Research, London NW7 1AA, United Kingdom
    Current affiliation:
    1. Neurology-CEDD, Glaxo-SmithKline, New Frontiers Science Park North, Third Avenue, Harlow, Essex CM19 5AW, UK
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  • Toshio Terashima

    Corresponding author
    1. Department of Anatomy, Kobe University School of Medicine, Kobe 650-0017, Japan
    • Toshio Terashima, Department of Anatomy, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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Abstract

Shaking Rat Kawasaki (SRK) is an autosomal recessive mutant rat that is characterized by cerebellar ataxia. Although previous studies indicated many points of similarity between this mutant rat and the reeler mouse, nonlaminated structures such as the facial nucleus have not been studied in this mutant rat. Nissl-stained sections through the brainstem showed that the cytoarchitecture of the facial, motor trigeminal, and ambiguus nuclei was abnormal in SRK, especially in the lateral cell group of the facial nucleus and the compact formation of the ambiguus nucleus. To examine whether orofacial motoneurons are also malpositioned in the SRK rat, horseradish peroxidase (HRP) was injected into the facial, masticatory, and abdominal esophageal muscles of the SRK rats and normal controls to label facial, trigeminal, and ambiguus motoneurons, respectively. HRP-labeled facial, trigeminal, and ambiguus motoneurons of the SRK rat were distributed more widely than those of their normal counterparts, as in the case of the reeler mouse, with the one exception that labeled facial motoneurons innervating the nasolabial muscle were distributed more widely in the ventrolateral-to-dorsomedial direction in comparison with those of the reeler mutant. These data demonstrate that nonlaminated structures in the brainstem of the SRK rat are affected severely, as is the case in the reeler mutant mouse. J. Comp. Neurol. 439:275–290, 2001. © 2001 Wiley-Liss, Inc.

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