Abstract
No direct evidence has been found for expression of functional AMPA receptors by dorsal root ganglion neurons despite immunocytochemical evidence suggesting they are present. Here we report evidence for expression of functional AMPA receptors by a subpopulation of dorsal root ganglion neurons. The AMPA receptors are most prominently located near central terminals of primary afferent fibers. AMPA and kainate receptors were detected by recording receptor-mediated depolarization of the central terminals under selective pharmacological conditions. We demonstrate that activation of presynaptic AMPA receptors by exogenous agonists causes inhibition of glutamate release from the terminals, possibly via primary afferent depolarization (PAD). These results challenge the traditional view that GABA and GABA(A) receptors exclusively mediate PAD, and indicate that PAD is also mediated by glutamate acting on presynaptically localized AMPA and kainate receptors.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Action Potentials / drug effects
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Action Potentials / physiology
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Afferent Pathways / cytology
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Afferent Pathways / drug effects
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Afferent Pathways / metabolism
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Animals
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Animals, Newborn
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Calcium Signaling / drug effects
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Calcium Signaling / physiology
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Cells, Cultured
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Excitatory Amino Acid Agonists / pharmacology
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Excitatory Amino Acid Antagonists / pharmacology
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GABA Antagonists / pharmacology
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GABA-A Receptor Antagonists
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Ganglia, Spinal / cytology
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Ganglia, Spinal / drug effects
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Ganglia, Spinal / metabolism*
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Glutamic Acid / metabolism*
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Intermediate Filament Proteins / metabolism
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Lectins
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Membrane Glycoproteins*
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Nerve Tissue Proteins / metabolism
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Neural Inhibition / drug effects
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Neural Inhibition / physiology*
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Neurons, Afferent / cytology
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Neurons, Afferent / drug effects
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Neurons, Afferent / metabolism*
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Peripherins
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / metabolism*
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Rats
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Receptors, AMPA / drug effects
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Receptors, AMPA / metabolism*
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Receptors, AMPA / ultrastructure
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Receptors, GABA-A / metabolism
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Spinal Nerve Roots / cytology
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Spinal Nerve Roots / drug effects
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Spinal Nerve Roots / metabolism
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology*
Substances
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Excitatory Amino Acid Agonists
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Excitatory Amino Acid Antagonists
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GABA Antagonists
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GABA-A Receptor Antagonists
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Intermediate Filament Proteins
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Lectins
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Membrane Glycoproteins
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Nerve Tissue Proteins
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Peripherins
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Receptors, AMPA
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Receptors, GABA-A
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Glutamic Acid
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glutamate receptor ionotropic, AMPA 2
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glutamate receptor ionotropic, AMPA 1