Abstract
The relative contribution of kainate receptors to ongoing glutamatergic activity is at present unknown. We report the presence of spontaneous, miniature, and minimal stimulation-evoked excitatory postsynaptic currents (EPSCs) that are mediated solely by kainate receptors (EPSC(kainate)) or by both AMPA and kainate receptors (EPSC(AMPA/kainate)). EPSC(kainate) and EPSC(AMPA/kainate) are selectively enriched in CA1 interneurons and mossy fibers synapses of CA3 pyramidal neurons, respectively. In CA1 interneurons, the decay time constant of EPSC(kainate) (circa 10 ms) is comparable to values obtained in heterologous expression systems. In both hippocampal neurons, the quantal release of glutamate generates kainate receptor-mediated EPSCs that provide as much as half of the total glutamatergic current. Kainate receptors are, therefore, key players of the ongoing glutamatergic transmission in the hippocampus.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Dynorphins / metabolism
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Electric Stimulation
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Excitatory Amino Acid Antagonists / pharmacology
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Excitatory Postsynaptic Potentials / drug effects
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Excitatory Postsynaptic Potentials / physiology*
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GABA Antagonists / pharmacology
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Glutamic Acid / metabolism*
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Hippocampus / cytology
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Hippocampus / drug effects
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Hippocampus / metabolism*
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Interneurons / cytology
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Interneurons / drug effects
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Interneurons / metabolism
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Kinetics
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Male
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Mossy Fibers, Hippocampal / drug effects
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Mossy Fibers, Hippocampal / metabolism
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Mossy Fibers, Hippocampal / ultrastructure
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Organ Culture Techniques
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / metabolism*
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Pyramidal Cells / cytology
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Pyramidal Cells / drug effects
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Pyramidal Cells / metabolism
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Rats
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Rats, Wistar
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Receptors, AMPA / antagonists & inhibitors
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Receptors, AMPA / metabolism*
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Receptors, Kainic Acid / antagonists & inhibitors
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Receptors, Kainic Acid / metabolism*
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Sodium Channel Blockers / pharmacology
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Synaptic Vesicles / drug effects
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Synaptic Vesicles / metabolism*
Substances
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Excitatory Amino Acid Antagonists
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GABA Antagonists
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Receptors, AMPA
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Receptors, Kainic Acid
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Sodium Channel Blockers
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Glutamic Acid
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Dynorphins