Abstract
Neurotransmitter is stored in synaptic vesicles and released by exocytosis into the synaptic cleft. One of the fundamental questions in central synaptic transmission is whether a quantal packet of transmitter saturates postsynaptic receptors. To address this question, we loaded the excitatory transmitter L-glutamate via whole-cell recording pipettes into the giant nerve terminal, the calyx of Held, in rat brainstem slices. This caused marked potentiations of both quantal and action potential-evoked EPSCs mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors. These results directly demonstrate that neither AMPA nor NMDA receptors are saturated by a single packet of transmitter, and indicate that vesicular transmitter content is an important determinant of synaptic efficacy.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Auditory Pathways / metabolism
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Auditory Pathways / ultrastructure
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Binding Sites / drug effects
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Binding Sites / physiology
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Cytosol / drug effects
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Cytosol / metabolism
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Dose-Response Relationship, Drug
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Excitatory Postsynaptic Potentials / drug effects
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Excitatory Postsynaptic Potentials / physiology*
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Exocytosis / drug effects
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Exocytosis / physiology*
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Glutamic Acid / metabolism*
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Glutamic Acid / pharmacology
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Olivary Nucleus / metabolism
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Olivary Nucleus / ultrastructure
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Organ Culture Techniques
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Pons / metabolism
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Pons / ultrastructure
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / metabolism*
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Presynaptic Terminals / ultrastructure
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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, Glutamate / drug effects
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Receptors, Glutamate / metabolism*
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Receptors, N-Methyl-D-Aspartate / drug effects
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Receptors, N-Methyl-D-Aspartate / metabolism
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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*
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Synaptic Vesicles / ultrastructure
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Temperature
Substances
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Receptors, AMPA
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Receptors, Glutamate
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Receptors, N-Methyl-D-Aspartate
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Glutamic Acid