Abstract
Until now, the only well documented, fast excitatory neurotransmitter in the brain has been glutamate. Although there is evidence for adenosine 5'-triphosphate (ATP) acting as a transmitter in the peripheral nervous system, suggestions for such a role in the central nervous system have so far not been supported by any direct evidence. Here we report the recording of evoked and miniature synaptic currents in the rat medial habenula. The fast rise time of the currents showed that they were mediated by a ligand-activated ion channel rather than a second messenger system, thus limiting the known transmitter candidates. Evidence was found for the presence on the cells of glutamate, gamma-aminobutyric acid, acetylcholine and ATP receptors, but not for 5-hydroxytryptamine (5HT3) or glycine receptors. The evoked currents were unaffected by blockers of glutamate, gamma-aminobutyric acid or acetylcholine receptors but were blocked by the ATP receptor-blocker, suramin and the desensitizing ATP receptor-agonist alpha,beta-methylene-ATP. Our evidence identifies for the first time synaptic currents in the brain, mediated directly by ATP receptors.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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6-Cyano-7-nitroquinoxaline-2,3-dione
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Acetylcholine / pharmacology
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Adenosine Triphosphate / analogs & derivatives
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Adenosine Triphosphate / pharmacology
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Adenosine Triphosphate / physiology*
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Animals
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Bicuculline / pharmacology
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Brain / physiology*
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Chlorocebus aethiops
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Evoked Potentials, Somatosensory / drug effects
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Ganglionic Blockers / pharmacology
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Glutamates / physiology
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Glutamic Acid
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Hexamethonium
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Hexamethonium Compounds / pharmacology
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In Vitro Techniques
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Ion Channels / physiology
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Kynurenic Acid / analogs & derivatives
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Kynurenic Acid / pharmacology
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Mecamylamine / pharmacology
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Quinoxalines / pharmacology
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Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
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Receptors, Neurotransmitter / drug effects
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Receptors, Neurotransmitter / physiology*
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Suramin / pharmacology
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Tetrodotoxin / pharmacology
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gamma-Aminobutyric Acid / physiology
Substances
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Ganglionic Blockers
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Glutamates
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Hexamethonium Compounds
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Ion Channels
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Quinoxalines
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Receptors, N-Methyl-D-Aspartate
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Receptors, Neurotransmitter
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Hexamethonium
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Glutamic Acid
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Tetrodotoxin
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gamma-Aminobutyric Acid
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Suramin
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Mecamylamine
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6-Cyano-7-nitroquinoxaline-2,3-dione
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Adenosine Triphosphate
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Kynurenic Acid
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Acetylcholine
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alpha,beta-methyleneadenosine 5'-triphosphate
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7-chlorokynurenic acid
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Bicuculline