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2003 Fiscal Year Final Research Report Summary

Physiological analyses of voltage-gated ion channels and their molecular identifications in sensory neurons.

Research Project

Project/Area Number 14580779
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Neuroscience in general
Research InstitutionFujita Health University

Principal Investigator

MIYACHI Ei-ichi  Fujita Health University, School of Medicine, Professor, 医学部, 教授 (90129685)

Co-Investigator(Kenkyū-buntansha) HORIGUCHI Masayuki  Fujita Health University, School of Medicine, Professor, 医学部, 教授 (70209295)
OHKUMA Ahito  Fujita Health University, School of Medicine, Research Associate, 医学部, 助手 (50329710)
KAWAI Fusao  Fujita Health University, School of Medicine, Associate professor, 医学部, 助教授 (20300725)
Project Period (FY) 2002 – 2003
Keywordssensory organ / retina / photoreceptor / retinal bipolar cell / olfactory cell / voltage-gated sodium channel / voltage-gated calcium channel / h channel
Research Abstract

All vertebrate photoreceptors, including those of humans, respond to light stimuli with a graded hyperpolarization, and are commonly thought to be non-spiking neurons. To examine whether human photoreceptors can elicit action potentials, we studied surgically excised human retina using the whole-cell patch-clamp recording technique. A small piece (diameter less than 1 mm) of retina was excised from patients with retinal detachment during the surgical procedure to re-attach the retina. All experiments were performed in compliance with the guideline of the Declaration of Helsinki and approved by the ethics committee of our institute. We found that photoreceptors express voltage-gated Na^+ channels, and generate Na^+ action potentials in response to membrane de polarization. This suggests that Na spikes might be elicited at the termination of a bright light stimulus. The Na action potentials would serve to amplify the release of neurotransmitter at the sudden offset of a bright light, and thus selectively amplify the "OFF" part of the light signal.
We also examined whether human rod photoreceptors express hyperpolarization-activated cationic currents (Ih). The slow inward current induced by hyperpolarization was markedly reduced by bath application of 3 mM Cs^+, a blocker of Ih,. Bath application of 3 mM Cs^+ also blocked the steady inward current. Our findings suggest that Ih becomes activated during large hyperpolarizations generated by bright illumination and may modify the waveform of the photovoltage.
The sense of vision in humans is quite robust and visual flickering is rarely experienced. Under current-clamp conditions, blockage by Cs^+, Tl^+ and ZD7288 of an h current hyperpolarized the resting potentials of cones and rods by 〜10-15 mV, and surprisingly generated spontaneous action potentials. We suggest that the h current may contribute to preventing visual flickering by inhibiting the generation of spontaneous Na^+ spikes in human cones and rods.

  • Research Products

    (15 results)

All Other

All Publications (15 results)

  • [Publications] Fusao Kawai: "Modulation by hyperpolarization-activated cationic currents of voltage responses in human rods."Brain Research. 943. 48-55 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Mahito Ohkuma: "Direct suppression by odorants of ionotropic glutamate receptors in newt retinal neurons."Journal of Neural Transmission. 109. 1365-1371 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Soh Hidaka: "Expression of gap junction connexin 36 in adult rat retinal ganglion cells."Journal of Interactive Neuroscience. 1. 1-21 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Ei-ichi Miyachi: "Voltage-gated ion channels human photoreceptors."Keio Journal of Medicine. 51 Suppl.1. 17 (2002)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kenji Narusuye: "Spike encoding of olfactory receptor cells."Neuroscience Research. 46. 407-413 (2003)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Hideki Imada: "Blood supply to the retina and the lens in the gerbil (Meriones unguiculatus)."Anatomical Science International. 78. 36-41 (2003)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Ei-ichi Miyachi(分担): "The Neural Basis of Early Vision"Springer-Verlag. 253 (2003)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kawai, F., Horiguchi M., Suzuki H., Miyachi.E.-I.: "Modulation by hyperpolarization-activated cationic currents of voltage responses in human rods."Brain Research. 943(1). 48-5 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Hidaka, S., Kate, T., Miyachi E.-J.: "Expression of gap junction connexin 36 in adult rat retinal ganglion cells."Journal of Integrative Neuroscience. 1(1). 3-22 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Ohkuma, M., Kawai, F., Miyachi.E.-I.: "Direct suppression by odorants of ionotropic glutamate receptors in newt retinal neurons."Journal of Neural Transmission. 109(11). 1365-1371 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Hideki Imada, Genzoh Isomura, Ei-ichi Miyachi: "Blood supply to the retina and lens in the gerbil (Meriones unguiculatus)."Anatomical Science International. 78(1). 36-41 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Kenji Narusuye, Fusao Kawai, Ei-ichi Miyachi: "Spike encoding of olfactory receptor cells."Neuroscience Research. 46(4). 407-413 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Ei-ichi Miyachi, Fusao Kawai: "Voltage-gated ion channels in human photoreceptors : Na^<+> and hyperpolarization -activated cation channels."In The Neural Basis of Early Vision, A.Kaneko (Ed.), (Springer). 5-14 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Soh Hidaka, Ei-ichi Miyachi: "Hornotypic gap junction connections between retinal amacrine cells."The Neural Basis of Early Vision, A.Kaneko (Ed.), (Springer). 126-133 (2003)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Mahito Ohkuma, Fusao Kawai, Ei-ichi Miyachi: "Suppression by odorants of voltage-gated and ligand-gated channels in retinal neurons."The Neural Basis of Early Vision, A.Kaneko (Ed.), (Springer). 143-146 (2003)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 2005-04-19  

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