1993 Fiscal Year Final Research Report Summary
Synaptic mechanisms in the outerplexiform layr of the vertebrate retina
| Project/Area Number |
04640670
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
動物発生・生理学
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| Research Institution | Department of Physiology, Keio University School of Medicine |
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Principal Investigator |
TAKAHASHI Kyoh-Ichi Department of Physiology, Keio University School of Medicine Research Associate, 医学部, 助手 (70138121)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Vertebrate / Retina / Synaptic mechanism / Outerplexiform layr / Ligand-gated receptor / Ion channel / Calcium channel / Glutamate |
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| Research Abstract |
For elucidating the synaptic mechanisms in the outerplexiform layr of the vertebrate retina, the physiological and biophysical properties of photoreceptors, bipolar cells and horizontal cells should be investigated. In an attempt to pursue this purpose, I studied on ligand-gated receptors and ion channels in cone-driven horizontal cells dissociated from the retina of the catfish (Ictalurus punctatus) with a conventional intracellular technique and a whole-cell patch-clamp technique.
1. The horizontal cell responded to an application of L-glutamate(Glu, 100mM) with depolarization. The Glu-induced depolarization was suppressed by an application of 2-amino-4-phosphonobutyric acid(APB 10 - 100 muM), which is known to be an agonist for a Glu receptor of ON-type bipolar cells. This suppression was modified by a change of intracellular proton concentration(pH).
2. Glu(1 - 100 muM) caused an intracellular acidification in a concentration-dependent manner, although the mechanism by which the cell was acidified remained to be solved. The acidification evoked by Glu inhibited an HVA calcium channel current. EC_<50> for pH inhibition of HVA current was pH 7.1 and the Hill coefficient was approximately 2.
From the above results, it is tempting to suggest that intracellular protons as a second messenger play an important role on regulation of ligand-gated receptors and ion channels. To confirm function of the intracellular protons, a further analysis will be needed.
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