ICHIKAWA Riyouichi

写真a

Affiliation

School of Medicine, Department of Anatomy (1)

Job title

Associate Professor
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Education 【 display / non-display 】

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    1990

    Hokkaido University  

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    1990

    Hokkaido University  

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Degree 【 display / non-display 】

  • PhD(Medical science)

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Professional Memberships 【 display / non-display 】

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    The Japanese Association of Anatomists

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    The Institute of Electronics

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    Information and Communication Engineers

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    Society for Neuroscience

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    日本エム・イー学会

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Affiliation 【 display / non-display 】

  • Sapporo Medical University   School of Medicine, 1st Dept.of Anatomy   Assistant Professor  

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Research Interests 【 display / non-display 】

  • 神経生物学 神経解剖学

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Papers 【 display / non-display 】

  • GluD2 Endows Parallel Fiber-Purkinje Cell Synapses with a High Regenerative Capacity

    Ryoichi Ichikawa, Kenji Sakimura, Masahiko Watanabe

    JOURNAL OF NEUROSCIENCE ( SOC NEUROSCIENCE )  36 ( 17 ) 4846 - 4858  2016.04  [Refereed]

    　View Summary

    Although injured axons usually do not regenerate in the adult CNS, parallel fibers (PFs) regenerate synaptic connections onto cerebellar Purkinje cells (PCs). In this study, we investigated the role of GluD2 in this regenerative process after PF transection using GluD2-knock-out (KO) mice. All dendritic spines on distal dendrites were innervated by PFs in sham-operated wild-type controls, whereas one-third were devoid of innervation in GluD2-KO mice. In both genotypes, a steep drop in the number of PF synapses occurred with a reciprocal surge in the number of free spines on postlesion day 1, when the PF territory aberrantly expanded toward the proximal dendrites. In wild-type mice, the territory and number of PF synapses were nearly fully restored to normal on postlesion day 7, although PF density remained low. Moreover, presynaptic and postsynaptic elements were markedly enlarged, and the PF terminal-to-PC spine contact ratio increased from 1:1 to 1:2 at most synapses. On postlesion day 30, the size and contact ratio of PF synapses returned to sham-operated control values and PF density recovered through the sprouting and elongation of PF collaterals. However, GluD2-KO mice showed neither a hypertrophic response nor territorial restoration 7 d postlesion, nor the recovery of PF axons or synapses on postlesion day 30. This suggests that PF wiring regenerates initially by inducing hypertrophic responses in surviving synaptic elements (hypertrophic phase), followed by collateral formation by PF axons and retraction of PF synapses (remodeling phase). Without GluD2, no transition to these regenerative phases occurs.

    DOI

  • Territories of heterologous inputs onto Purkinje cell dendrites are segregated by mGluR1-dependent parallel fiber synapse elimination

    Ichikawa R, Hashimoto K, Miyazaki T, Uchigashima M, Yamasaki M, Aiba A, Kano M, Watanabe M

    Proc Natl Acad Sci U S A   113   2282 - 2287  2016  [Refereed]

  • Developmental Switching of Perisomatic Innervation from Climbing Fibers to Basket Cell Fibers in Cerebellar Purkinje Cells

    Ryoichi Ichikawa, Miwako Yamasaki, Taisuke Miyazaki, Kohtarou Konno, Kouichi Hashimoto, Haruyuki Tatsumi, Yoshiro Inoue, Masanobu Kano, Masahiko Watanabe

    JOURNAL OF NEUROSCIENCE ( SOC NEUROSCIENCE )  31 ( 47 ) 16916 - 16927  2011.11  [Refereed]

    　View Summary

    In early postnatal development, perisomatic innervation of cerebellar Purkinje cells (PCs) switches from glutamatergic climbing fibers (CFs) to GABAergic basket cell fibers (BFs). Here we examined the switching process in C57BL/6 mice. At postnatal day 7 (P7), most perisomatic synapses were formed by CFs on to somatic spines. The density of CF-spine synapses peaked at P9, when pericellular nest around PCs by CFs was most developed, and CF-spine synapses constituted 88% of the total perisomatic synapses. Thereafter, CF-spine synapses dropped to 63% at P12, 6% at P15, and <1% at P20, whereas BF synapses increased reciprocally. During the switching period, a substantial number of BF synapses existed as BF-spine synapses (37% of the total perisomatic synapses at P15), and free spines surrounded by BFs or Bergmann glia also emerged. By P20, BF-spine synapses and free spines virtually disappeared, and BF-soma synapses became predominant (88%), thus attaining the adult pattern of perisomatic innervation. Parallel with the presynaptic switching, postsynaptic receptor phenotype also switched from glutamatergic to GABAergic. In the active switching period, particularly at P12, fragmental clusters of AMPA-type glutamate receptor were juxtaposed with those of GABA(A) receptor. When examined with serial ultrathin sections, immunogold labeling for glutamate and GABA(A) receptors was often clustered beneath single BF terminals. These results suggest that a considerable fraction of somatic spines is succeeded from CFs to BFs and Bergmann glia in the early postnatal period, and that the switching of postsynaptic receptor phenotypes mainly proceeds under the coverage of BF terminals.

    DOI

  • Translocation of a "Winner" climbing fiber to the Purkinje cell dendrite and subsequent eliminatio of "losers" from the soma in developing cerebellum

    Hashimoto K, Ichikawa R, Kitamura K, Watanabe M, Kano M

    Neuron   6   106 - 118  2009  [Refereed]

  • Distal Extension of Climbing Fiber Territory and Multiple Innervation Caused by Aberrant Wiring to Adjacent Spiny Branchlets in Cerebellar Purkinje Cells Lacking Glutamate Receptor GluR2

    Ichikawa R, Miyazaki T, Kano M, Hashikawa T, Tatsumi H, Sakimura K, Mishina M, Inoue Y, Watanabe M

    J Neurosci,   22   8487 - 8503  2002  [Refereed]

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Misc 【 display / non-display 】

  • Transient neonatal expression of NR2B/2D subunit mRNAs of the N-methyl-D-aspartate receptor in the parasympathetic preganglionic neurons in the rat spinal cord.

    Brain Res Dev Brain Res   140   263 - 8  2003

    DOI

  • Distal extension of climbing fiber territory and multiple innervation caused by aberrant wiring to adjacent spiny branchlets in cerebellar Purkinje cells lacking glutamate receptor delta 2.

    J Neurosci   22   8487 - 503  2002

  • Ovariectomy attenuates hyperpolarization and relaxation mediated by endothelium-derived hyperpolarizing factor in female rat mesenteric artery: a concomitant decrease in connexin-43 expression.

    J Cardiovasc Pharmacol   40   938 - 48  2002

    DOI

  • Roles of glutamate receptor delta 2 subunit (GluRdelta 2) and metabotropic glutamate receptor subtype 1 (mGluR1) in climbing fiber synapse elimination during postnatal cerebellar development.

    J Neurosci   21   9701 - 12  2001

  • Enhancement of hippocampal LTP, reference memory and sensorimotor gating in mutant mice lacking a telencephalon-specific cell adhesion molecule.

    Eur J Neurosci   13   179 - 89  2001

    DOI

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Awards 【 display / non-display 】

  • 北海道医学会賞

    1999  

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Research Projects 【 display / non-display 】

  • 小脳プルキンエ細胞上のシナプス構築形成機構の解明

  • リーラーマウス大脳皮質投射神経細胞の形態形成の解明

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