1988 Fiscal Year Final Research Report Summary
Transmitter substances of retinal neurons
| Project/Area Number |
61440026
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Okazaki National Research Institute |
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Principal Investigator |
KANEKO Akimichi Professor, National Institute for Physiological Sciences, 生理学研究所, 教授 (00051491)
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| Co-Investigator(Kenkyū-buntansha) |
TAUCHI Masaki Assistant Professor, National Institute for Physiological Sciences, 生理学研究所, 助手 (00075425)
TACHIBANA Masao Assistant Professor, National Institute for Physiological Sciences, 生理学研究所, 助手 (60132734)
OHTSUKA Teruya Associate Professor, National Institute for Physiological Sciences, 生理学研究所, 助教授 (10051814)
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| Project Period (FY) |
1986 – 1988
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| Keywords | retina / isolated cells / photoreceptor / bipolar cell / gamma-aminobutyric acid / glutamate / calcium current / goldfish / turtle / マウス |
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| Research Abstract |
Knowledge on the synapic transmission is essential for the understanding of a nervous system. The aim of the present study was to understand the action of synaptic transmitter in the vertebrate retina. We recorded membrane currents of solitary neurons by using patch clamp technique in the whole cell configuration. Cells were dissociated from the retina of goldfish, turtle and mouse. The following is a list of major findings.
1. Uptake of L-glutamate by photoreceptors. It is now generally accepted that L-glutamate is released from photoreceptors. L-Glutamate is taken up by photoreceptors by a transport system. Electrochemical gradient of Na^+ is the enegy source for transport; 3 Na^+ are co-transported with each glutamate modecule. Thus, this system is electrogenic, causing depolarization in all subtypes of photoreceptors. It is likely that this mechanism contribute in excitatory interaction among heterologous photoreceptors.
2 Inhibition mediated by -aminobutyric acid (GABA) from amacrin
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e cell to bipolar cell. GABA induced hyper-polarization in goldfish bipolar cells by opening chloride channels mediated by GABAalpha receptor.
3. Transient calcium current of mouse bipolar cells. Calcium current (I_<ca>) in mouse bipolar cells is T-type showing rapid inactivation. I_<ca> flowed through the axon terminal as well as the soma. It is hypothesized that the transmitter release from bipolar cell terminal is also transient. Thus, I_<ca> of mouse bipolar cells may contribute in shaping transient light evoked responses in amacrine and ganglion cells.
4. Connectivity between photoreceptors and horizontal cells in the turtle retina. Subtypes of turtle cones are readily identified morphologically by their colored oil droplets. Using this index, we analyzed connectivity of photoreceptors and horizontal cells. Contrary to the general belief, red-sensitive cones were found to make direct connection to H_2 and H_3 horizontal cells. Color vision models are discussed based on this new finding. Less
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