Abstract
L-Glutamate (Glu)-induced current responses were studied in 119 isolated OFF-type bipolar cells of the cat retina. Cells were recorded by the patch clamp technique in the whole-cell configuration. Glu induced a current carried by alkali metal ions and divalent cations with a permeability ratio of PNa:PK:PCs:PCa = 1:0.94:1.32:0.57. Sensitivity to Glu was highest in the dendritic region. Kainate and AMPA worked as potent agonists, but neither APB, L-aspartate, ACPD, nor NMDA (all at 100 microM) was effective. The Glu-induced response was antagonized by > 1 microM CNQX. We inferred that OFF-type bipolar cells have a non-NMDA receptor channel that is permeable to alkali metal ions with low selectivity, but not NMDA receptor or metabotropic Glu receptor.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
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Aminobutyrates / pharmacology
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Animals
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Aspartic Acid / pharmacology
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Calcium / metabolism
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Cats
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Chlorides / metabolism
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Cycloleucine / analogs & derivatives
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Cycloleucine / pharmacology
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Dose-Response Relationship, Drug
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Glutamic Acid / pharmacology*
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Glycine / pharmacology
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In Vitro Techniques
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Ion Transport / drug effects
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Kainic Acid / pharmacology
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Membrane Potentials / drug effects
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N-Methylaspartate / pharmacology
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Neurons / drug effects*
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Neurons / metabolism
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Patch-Clamp Techniques
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Potassium / metabolism
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Retina / cytology*
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Retina / drug effects
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Retina / metabolism
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Retinal Cone Photoreceptor Cells / physiology
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Sodium / metabolism
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alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology
Substances
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Aminobutyrates
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Chlorides
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Cycloleucine
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1-amino-1,3-dicarboxycyclopentane
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Aspartic Acid
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Glutamic Acid
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N-Methylaspartate
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6-Cyano-7-nitroquinoxaline-2,3-dione
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alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
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Sodium
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2-amino-4-phosphonobutyric acid
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Potassium
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Kainic Acid
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Calcium
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Glycine