2006 Fiscal Year Final Research Report Summary
Analyses of the physiological functions of voltage-dependent ion channels in sensory organs and their expressions in the process of regeneration and differentiation in sensory organs.
| Project/Area Number |
17500217
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Neuroscience in general
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| Research Institution | FUJITA HEALTH UNIVERSITY |
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Principal Investigator |
MIYACHI Eiichi FUJITA HEALTH UNIVERSITY, School of Medicine, Professor, 医学部, 教授 (90129685)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAI Fusao FUJITA HEALTH UNIVERSITY, School of Medicine, Associate Professor, 医学部, 助教授 (20300725)
OHKUMA Mahito FUJITA HEALTH UNIVERSITY, School of Medicine, Assistant Professor, 医学部, 講師 (50329710)
IMADA Hideki FUJITA HEALTH UNIVERSITY, School of Medicine, Research Associate, 医学部, 助手 (70387710)
WATANABE Masami FUJITA HEALTH UNIVERSITY, School of Medicine, Visiting Assistant Professor, 医学部, 客員講師 (10093486)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Sensory organ / retinal bipolar cell / retinal ganglion cell / patch-clamp technique / voltage-dependent Na+ channel / optic nerve axotomy / regeneration / acetycholine |
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| Research Abstract |
(1) The whole-cell patch-clamp recording was performed at inner nuclear layer in the fragments of the human retina. Under voltage-clamp conditions, depolarizing voltage steps induced a fast transient inward current in several bipolar cells. This current was activated from-60 mV to +10 mV (maximal at-20 mV) and inactivated within 5 ms. And the current was blocked by TTX. These results suggest that human retinal bipolar cells express voltage-gated Na+ channels. The hyperpolarization-activated cation current (h current) was not observed in human retinal bipolar cells (n = 0/16), while h currents were observed in human photoreceptors. Next, we performed a single-cell RT-PCR analysis to test whether bipolar cells express the Na+ channel transcript. Nav1.2 channels identified from retinal mRNA were observed in 5 of 6 bipolar cells. This suggests that human bipolar cells express Nav1.2 channels as well as human photoreceptors.
(2) Acetylcholine receptors are known to be expressed in developmental and regenerative process of retinal ganglion cells in newts and other species. We performed Fura-2 based calcium imaging of retinal ganglion cells in adult cats to examine, whether acetylcholine responses were detected in retinal ganglion cells at various degenerating or regenerating stages after axotomy. Calcium imaging of retinal ganglion cells showed that bath application of 100 μM carbachol, an acetylcholine receptor agonist, rose intracellular calcium concentration in 22% of ganglion cells in the intact retina. Three days after axotomy, 85% of examined ganglion cells responded to carbachol. However, no ganglion cells responded to carbachol 7-15 days after axotomy. Responsiveness to acetylcholine recovered in axonal regenerated surviving ganglion cells (17%). These results suggest that acetylcholine may have neurotrophic effect on surviving ganglion cells, and that acetylcholine may be a key marker for neuronal degeneration /regeneration in cat retinal ganglion cells.
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Research Products
(12 results)
