1994 Fiscal Year Final Research Report Summary
MOLECULAR MECHANISM OF HYPERPOLARIZATION OF ON-BIPOLAR CELLS IN RETINA
| Project/Area Number |
05454634
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biophysics
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| Research Institution | HIMEJI INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
TSUDA Motoyuki HIMEJI INSTITUTE OF TECHNOLOGY,FACULTY OF SCIENCE,PROFESSOR, 理学部, 教授 (60045458)
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| Co-Investigator(Kenkyū-buntansha) |
NIKKAWA Satoshi HIMEJI INSTITUTE OF TECHNOLOGY,FACULTY OF SCIENCE,ASSISTANT PROFESSOR, 理学部, 助手 (90244681)
NAKAGAWA Masashi HIMEJI INSTITUTE OF TECHNOLOGY,FACULTY OF SCIENCE,ASSISTANT PROFESSOR, 理学部, 助手 (00212085)
IWASA Tatsuo HIMEJI INSTITUTE OF TECHNOLOGY,FACUTLY OF SCIENCE,ASSOCIATE PROFESSOR, 理学部, 助教授 (00133926)
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| Project Period (FY) |
1993 – 1994
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| Keywords | RETINA / GULTAMATE RECEPTOR / SECOND NEURON / HYPERPOLARIZAION / BIPOLAR CELL / G-PROTEIN / SYNAPSE / RECEPTOR |
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| Research Abstract |
Light reduce the release of glutamate from photoreceptor cell, resulting in opening of cation channels on on-bipolar cell and subsequent depolarization of the cell. In this respect, retinal onbipolar cell is a novel neuron which hyperpolarizes on contact with neurotransmitter molecules. Electrophysiological studies showed that cGMP act as the second messenger mediating the action of glutamate through the G protein that striking similarities to transduction in photoreceptors. In order to elucidate molecular mechanism of hyperpolarization of on-bipolar cell, we studied signal coupling proteins of on-bipolar cell in bovine retina.
GTP-binding protein (G protein) linking to metabotropic glutamate receptor of bovine retinal on-bipolar cell was studied by use of pharmacologically selective ligands, 2-amino-4-phosphonobutyric acid (APB) on bacteria toxin-catalyzed ADP-ribosylation and GTP S-binding. In contrast to the electrophysiological finding reported, G-protein coupling to APB-sensitive glutamate receptor served as a substrate for pertussis toxin but did not for cholera toxin. Several glutamate analogues effective on on-bipolar cell, as well as APB,increased GTP S binding to retinal membranes devoid of rod outer segments. The enhancement of GTP S binding by APB was completely abolished when the membranes were pretreated with pertussis toxin and NAD.These results suggest that, in retinal on-bipolar cell, the G-protein which couples metabotropic glutamate receptor to hyperpolarizing response of the cell is sensitive to pertussis toxin.
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[Publications] Liang, J., Steinberg, G., Livnah, N., Sheves, M., Ebrey, T., Tsuda, M.(1994): "The pKa of the Protonated Schiff base of Gecko Cone and Octopus Visual Pigments." Biophys.J.67 : 2. 848-854
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