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Single-vesicle imaging reveals that synaptic vesicle exocytosis and endocytosis are coupled by a single stochastic mode

Balaji, J., Ryan, T.A.
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.51 pp. 20576-20581
action potentials, endocytosis, exocytosis, image analysis, nerve tissue, stochastic processes, synaptic vesicles
The nature of synaptic vesicle recycling at nerve terminals has been a subject of considerable debate for >35 years. Here, we report the use of an optical strategy that allows the exocytosis and retrieval of synaptic components to be tracked in real time at single-molecule sensitivity in living nerve terminals. This approach has allowed us to examine the recycling of synaptic vesicles in response to single action potentials. Our results show that, after exocytosis, individual synaptic vesicles are retrieved by a stochastic process with an exponential distribution of delay times, with a mean time of [almost equal to]14 s. We propose that evidence for fast endocytosis, such as that proposed to support the presence of kiss-and-run, is likely explained by the stochastic nature of a slower process.