Abstract
The enhancement of synaptic exocytosis is one form of long-term potentiation (LTP) of synaptic transmission. As possible mechanisms underlying this enhancement, increases in the release probability and/or the number of release sites are suggested. To obtain direct evidence for the increase in the number of functional release sites induced by protein kinase A (PKA) cascade, we attempted to visualize functional release sites using styryl dyes, FM4-64 and FM1-43, and investigated the effects of PKA on the release sites. A PKA activator FSK increased the number of active release sites by approximately 20-30%. A direct PKA activator, Sp-cAMPS, showed the same effect, which was blocked by a PKA inhibitor, KT5720, suggesting that this effect was mediated by PKA. This PKA-dependent increase in the number of release sites requires Ca(2+) in the bath solution, and Sr(2+) can not be a substitute for Ca(2+). Since the number of functional release sites is approximately half the total number of synaptophysin-immunoreactive sites, the PKA dependent activation of silent release sites of DG neuron terminals is suggested.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Calcium / metabolism
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Calcium / pharmacology
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Carbazoles*
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Cells, Cultured / cytology
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Cells, Cultured / drug effects
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Cells, Cultured / metabolism
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Colforsin / analogs & derivatives
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Colforsin / pharmacology
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Cyclic AMP / analogs & derivatives*
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Cyclic AMP / metabolism*
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Cyclic AMP / pharmacology
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Dentate Gyrus / cytology
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Dentate Gyrus / drug effects
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Dentate Gyrus / enzymology*
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Enzyme Inhibitors / pharmacology
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Exocytosis / drug effects
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Exocytosis / physiology*
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Extracellular Space / drug effects
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Extracellular Space / metabolism
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Indoles / pharmacology
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Long-Term Potentiation / physiology
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Neurotransmitter Agents / metabolism*
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Potassium Chloride / pharmacology
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / enzymology*
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Presynaptic Terminals / ultrastructure
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Protein Kinases / drug effects
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Protein Kinases / metabolism*
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Pyrroles / pharmacology
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Rats
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Strontium / pharmacology
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology*
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Thionucleotides / pharmacology
Substances
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Carbazoles
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Enzyme Inhibitors
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Indoles
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Neurotransmitter Agents
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Pyrroles
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Thionucleotides
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Colforsin
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adenosine-3',5'-cyclic phosphorothioate
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KT 5720
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Potassium Chloride
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Cyclic AMP
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Protein Kinases
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Calcium
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Strontium