Bulk Synaptic Vesicle Endocytosis Is Rapidly Triggered during Strong Stimulation

Bulk endocytosis in central nerve terminals is activated by strong stimulation; however, the speed at which it is initiated and for how long it persists is still a matter of debate. To resolve this issue, we performed a characterization of bulk endocytic retrieval using action potential trains of in...

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Bibliographic Details
Published in:The Journal of neuroscience 2008-06, Vol.28 (26), p.6627-6632
Main Authors: Clayton, Emma L, Evans, Gareth J. O, Cousin, Michael A
Format: Article
Language:English
Subjects:
Action Potentials - physiology
Animals
Animals, Newborn
Brief Communications
Cells, Cultured
Electric Stimulation
Endocytosis - physiology
Fluorescent Dyes
Horseradish Peroxidase
Presynaptic Terminals - physiology
Presynaptic Terminals - ultrastructure
Rats
Rats, Sprague-Dawley
Synaptic Membranes - physiology
Synaptic Membranes - ultrastructure
Synaptic Transmission - physiology
Synaptic Vesicles - physiology
Synaptic Vesicles - ultrastructure
Time Factors
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Summary:Bulk endocytosis in central nerve terminals is activated by strong stimulation; however, the speed at which it is initiated and for how long it persists is still a matter of debate. To resolve this issue, we performed a characterization of bulk endocytic retrieval using action potential trains of increasing intensity. Bulk endocytosis was monitored by the loading of the fluorescent dyes FM2-10 and FM1-43, uptake of tetramethylrhodamine-dextran (40 kDa), or morphological analysis of uptake of the fluid-phase marker horseradish peroxidase. When neuronal cultures were subjected to mild stimulation (200 action potentials at 10 Hz), bulk endocytosis was not observed using any of our assay systems. However, when more intense trains of action potentials (400 or 800 action potentials at 40 and 80 Hz, respectively) were applied to neurons, bulk endocytosis was activated immediately, with the majority of bulk endocytosis complete by the end of stimulation. This contrasts with single synaptic vesicle endocytosis, the majority of which occurred after stimulation was terminated. Thus, bulk endocytosis is a fast event that is triggered during strong stimulation and provides the nerve terminal with an appropriate mechanism to meet the demands of synaptic vesicle retrieval during periods of intense synaptic vesicle exocytosis.
ISSN:0270-6474
1529-2401
DOI:10.1523/JNEUROSCI.1445-08.2008