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The kinetics of nerve-evoked quantal secretion
1CNR Centre of Cytopharmacology, Department of Neurosciences, Dibit, Italy.
Summary
Neurotransmitter release involves a reversible fusion complex assembly. The action potential deterministically triggers synchronous release from armed vesicles, revising current quantal release models.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Current models describe neurotransmitter release via a binomial system.
- Existing models struggle to reconcile statistical and kinetic data.
- Vesicle docking and fusion machine formation precede release.
Purpose of the Study:
- To revise the biophysical model of quantal neurotransmitter release.
- To explain discrepancies in statistical and kinetic studies of release.
- To propose a new schema for vesicle fusion complex assembly and release.
Main Methods:
- Analysis of transient silencing of release post-action potential.
- Investigation of asynchronous exocytosis at intermediate fusion stages.
- Examination of factors regulating fusion complex assembly and competence.
Main Results:
- Transient silencing of release occurs after synchronous release.
- Vesicle fusion complex assembly is a reversible, stochastic process.
- Asynchronous exocytosis occurs at intermediate stages, regulated by factors like divalent cations.
- Armed vesicles are competent for synchronous release only at specific sites.
- Action potential triggers deterministic, synchronous discharge of armed vesicles.
Conclusions:
- The fusion complex requires a specific conformation for synchronous evoked fusion.
- This revised model reconciles statistical and kinetic data during repetitive stimulation.
- The model explains toxin and genetic manipulation effects on release synchronization.