Abstract
Adenosine triphosphate is released into the synaptic cleft of the neuromuscular junction during normal synaptic transmission, and in much greater quantities following injury and ischaemia. There is much data to suggest roles for presynaptic P2 receptors but little to demonstrate which specific receptor subunits are present. Here we show P2X7 receptor subunits on presynaptic motor nerve terminals from birth, but no evidence for P2X1, P2X2, P2X3, P2X4, P2X5 or P2X6 receptor subunits. Further, P2X receptor subunits are present as multimeric, membrane-inserted receptors. A selective agonist, 2'-3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP: 100 microM), triggers vesicle release from motor nerve terminals, which is blocked by P2X7RS-specific concentrations of periodate oxidised ATP (OxATP: 100 microM) and brilliant blue G (BBG: 1 microM), but not by suramin (100 microM). Vesicle release is enhanced in the absence of extracellular divalent cations and occurs through activation of the ion channel and not any associated large pore, as we failed to label nerve terminals with large membrane-impermeant molecules after addition of BzATP. We conclude that a P2X7-like receptor is present at mouse motor nerve terminals, and that their activation promotes vesicle release.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / analogs & derivatives*
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Adenosine Triphosphate / metabolism*
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Adenosine Triphosphate / pharmacology
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Animals
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Benzenesulfonates / pharmacology
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Cations, Divalent / metabolism
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Ion Channels / drug effects
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Ion Channels / metabolism
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Mice
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Mice, Inbred C57BL
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Microscopy, Electron, Transmission
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Motor Neurons / drug effects
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Motor Neurons / metabolism*
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Motor Neurons / ultrastructure
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Muscle, Skeletal / innervation*
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Neuromuscular Junction / drug effects
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Neuromuscular Junction / metabolism*
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Neuromuscular Junction / ultrastructure
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Platelet Aggregation Inhibitors / pharmacology
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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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Protein Subunits / metabolism
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Purinergic P2 Receptor Agonists
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Purinergic P2 Receptor Antagonists
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Receptors, Purinergic P2 / metabolism*
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Receptors, Purinergic P2X7
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Synaptic Membranes / drug effects
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Synaptic Membranes / metabolism
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Synaptic Membranes / ultrastructure
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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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Time Factors
Substances
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Benzenesulfonates
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Cations, Divalent
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Ion Channels
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P2rx7 protein, mouse
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Platelet Aggregation Inhibitors
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Protein Subunits
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Purinergic P2 Receptor Agonists
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Purinergic P2 Receptor Antagonists
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Receptors, Purinergic P2
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Receptors, Purinergic P2X7
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periodate-oxidized adenosine 5'-triphosphate
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3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate
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Adenosine Triphosphate
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brilliant blue