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Exact Distribution of the Quantal Content in Synaptic Transmission
Krishna Rijal1, Nicolas I C Müller2, Eckhard Friauf2
1Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Physical Review Letters
|June 15, 2024
Summary
The quantal content distribution, crucial for synaptic transmission, is revealed to be binomial for fixed-interval action potentials but nonbinomial for Poisson inputs. This finding clarifies neurotransmitter release dynamics.
Area of Science:
- Neuroscience
- Computational Biology
- Biophysics
Background:
- Synaptic transmission involves the release of neurotransmitters via synaptic vesicles (SVs).
- Quantal content, the number of SVs released per action potential (AP), is typically modeled as binomial.
- The replenishment of readily releasable SVs is stochastic, complicating the quantal content distribution.
Purpose of the Study:
- To derive the exact probability distribution of quantal content under general stochastic AP inputs.
- To investigate how different AP input patterns (fixed interval vs. Poisson) affect quantal content distribution.
- To provide a framework for extracting synaptic parameters from experimental data.
Main Methods:
- Mathematical derivation of quantal content distribution for general stochastic AP inputs.
- Theoretical analysis of quantal content distribution for fixed-interval and Poisson AP trains.
- Comparison of theoretical predictions with electrophysiological recordings from MNTB-LSO synapses.
Main Results:
- The exact quantal content distribution is derived for steady-state stochastic AP inputs.
- A binomial distribution for quantal content is proven for fixed-interval AP trains.
- A nonbinomial distribution is demonstrated for Poisson AP trains.
- Exact moments of quantal content are derived for Poisson and other general cases.
Conclusions:
- The quantal content distribution is input-dependent, deviating from the simple binomial model under certain conditions.
- The derived mathematical framework allows for precise modeling of neurotransmitter release.
- This work provides tools to estimate synaptic model parameters from experimental measurements of quantal content.
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