Abstract
1. Whole-cell clamp experiments on Purkinje neurons in rat cerebellar slices were used to test whether glutamate transporters, detected immunocytochemically in the somata and dendrites of the cells, are functional in the cell surface membrane, and to investigate their role in terminating synaptic transmission. 2. A membrane current was detected with the pharmacology, voltage and ion dependence of a glutamate uptake current. Part of the current was generated by an anion conductance activated when uptake occurs. 3. With sodium and glutamate inside the cell, raising the external potassium concentration generated an outward current attributable to reversed operation of glutamate transporters. 4. The magnitude of the uptake current suggested that Purkinje cell transporters could help to terminate transmission at the climbing and parallel fibre to Purkinje cell synapses. Reducing postsynaptic glutamate uptake with intracellular D-aspartate prolonged the climbing fibre EPSC. 5. These data establish the existence of functional postsynaptic glutamate transporters, show that they contribute to terminating synaptic transmission, and suggest that they may play a role in the preferential death of Purkinje cells in ischaemia.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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2-Amino-5-phosphonovalerate / pharmacology
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6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
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Animals
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Aspartic Acid / pharmacology
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Benzoates / pharmacology
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Cycloleucine / analogs & derivatives
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Cycloleucine / pharmacology
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Electrophysiology
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Excitatory Amino Acid Antagonists / pharmacology
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Glutamic Acid / pharmacokinetics*
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Glycine / analogs & derivatives
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Glycine / pharmacology
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Ion Channel Gating / physiology
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Kynurenic Acid / pharmacology
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Monosaccharide Transport Proteins / metabolism
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Neuroprotective Agents / pharmacology
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Purkinje Cells / metabolism*
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Purkinje Cells / physiology
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Purkinje Cells / ultrastructure
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Rats
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Receptors, Metabotropic Glutamate / antagonists & inhibitors
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Tetrodotoxin / pharmacology
Substances
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Benzoates
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Excitatory Amino Acid Antagonists
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Monosaccharide Transport Proteins
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Neuroprotective Agents
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Receptors, Metabotropic Glutamate
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Cycloleucine
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1-amino-1,3-dicarboxycyclopentane
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alpha-methyl-4-carboxyphenylglycine
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Aspartic Acid
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Glutamic Acid
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Tetrodotoxin
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6-Cyano-7-nitroquinoxaline-2,3-dione
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2-Amino-5-phosphonovalerate
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Kynurenic Acid
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Glycine