Abstract
All-amacrine cells are crucial interneurons in the rod pathway of the mammalian retina. They receive input synapses from rod bipolar cells and make electrical output synapses into the ON-pathway and glycinergic chemical synapses into the OFF-pathway. Whole-cell currents from more than 50 voltage-clamped All-amacrine cells were recorded in a slice preparation of the rat retina. The recorded cells were identified by intracellular staining with Lucifer yellow. Spike-like potentials could be elicited upon depolarization by current injection. A voltage-activated, fast, TTX-sensitive, inward Na+ current was identified. A prominent outward K+ current could be suppressed by tetraethylammonium. GABA as well as glycine activated Cl- channels, which could be blocked by bicuculline and strychnine, respectively. Four agonists of excitatory amino acid receptors--kainate (KA), AMPA, 2-amino-4-phosphonobutyrate (APB), and NMDA--were tested. Inward currents at holding potentials of VH = -70 mV were found by application of KA and AMPA but not by application of APB and NMDA. These currents could be blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). ACh did not evoke any current responses.
MeSH terms
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4-Aminopyridine / pharmacology
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6-Cyano-7-nitroquinoxaline-2,3-dione
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Aminobutyrates / pharmacology
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Animals
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Cobalt / pharmacology
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Electrophysiology / methods
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Glutamates / pharmacology
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Glutamic Acid
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Glycine / pharmacology
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Ibotenic Acid / analogs & derivatives
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Ibotenic Acid / pharmacology
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In Vitro Techniques
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Ion Channel Gating / drug effects
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Ion Channels / drug effects
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Ion Channels / physiology*
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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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Potassium Channels / drug effects
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Potassium Channels / physiology
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Quinoxalines / pharmacology
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Rats
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Receptors, Amino Acid / drug effects
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Receptors, Amino Acid / physiology
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Retina / cytology*
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Retina / drug effects
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Retina / physiology*
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Retinal Ganglion Cells / physiology
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Sodium Channels / physiology
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Strychnine / pharmacology
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Synapses / drug effects
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Synapses / physiology
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Tetraethylammonium
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Tetraethylammonium Compounds / pharmacology
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Tetrodotoxin / pharmacology
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alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
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gamma-Aminobutyric Acid / pharmacology*
Substances
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Aminobutyrates
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Glutamates
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Ion Channels
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Potassium Channels
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Quinoxalines
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Receptors, Amino Acid
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Sodium Channels
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Tetraethylammonium Compounds
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Ibotenic Acid
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Cobalt
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Glutamic Acid
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Tetrodotoxin
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gamma-Aminobutyric Acid
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N-Methylaspartate
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Tetraethylammonium
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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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4-Aminopyridine
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2-amino-4-phosphonobutyric acid
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Strychnine
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Kainic Acid
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Glycine