Abstract
1. We have studied exocytosis and endocytosis in the synaptic terminal of salamander rods using a combination of Ca2+ imaging, capacitance measurement and the photolysis of Ca2+ buffers. 2. The average cytoplasmic Ca2+ concentration at the dark resting potential was 2-4 microM. 3. An average cytoplasmic Ca2+ concentration of 2-4 microM maintained a high rate of continuous exocytosis and endocytosis. 4. Changes in the rate of exocytosis were followed in less than 0.7 s by compensatory changes in the rate of endocytosis. 5. Vesicle cycling in the rod synapse is specialized for graded transmission and differs from that previously described for synapses that release synchronized bursts of transmitter.
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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Acetates / metabolism
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Aniline Compounds / metabolism
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Animals
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Calcium / analysis
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Chelating Agents / metabolism
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Chelating Agents / pharmacology
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Cytoplasm / chemistry
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Diazonium Compounds
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Electrophysiology
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Endocytosis / physiology*
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Ethylenediamines / metabolism
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Exocytosis / physiology*
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Fluorescent Dyes
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Light
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Membrane Potentials / physiology
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Microscopy, Fluorescence
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Phenoxyacetates
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Photolysis
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Retinal Rod Photoreceptor Cells / cytology*
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Retinal Rod Photoreceptor Cells / metabolism
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Synapses / metabolism
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Synaptic Vesicles / metabolism
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Urodela / physiology*
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Xanthenes / metabolism
Substances
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Acetates
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Aniline Compounds
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Chelating Agents
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Diazonium Compounds
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Ethylenediamines
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Fluorescent Dyes
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Phenoxyacetates
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Xanthenes
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diazo-2
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DM-nitrophen
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Fluo-3
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Calcium