Quantal analysis of excitatory postsynaptic currents at the hippocampal mossy fiber-CA3 pyramidal cell synapse | JoVE Visualize

Quantal analysis of excitatory postsynaptic currents at the hippocampal mossy fiber-CA3 pyramidal cell synapse

E von Kitzing¹, P Jonas, B Sakmann

¹Department of Cell Physiology, Max-Planck-Institute for Medical Research, Heidelberg, Germany.

Advances in Second Messenger and Phosphoprotein Research|January 1, 1994

View abstract on PubMed

Summary

Researchers analyzed hippocampal mossy fiber-CA3 synapses to understand quantal events. They found that postsynaptic factors significantly influence unitary excitatory postsynaptic current amplitudes, suggesting a more complex release mechanism.

Area of Science:

Neuroscience
Synaptic Plasticity
Computational Neuroscience

Background:

Mossy fiber (MF) to CA3 pyramidal cell synapses in the hippocampus are crucial for learning and memory.
Understanding the quantal properties of neurotransmitter release at these synapses is essential for deciphering synaptic function.

Purpose of the Study:

To analyze unitary excitatory postsynaptic current (EPSC) amplitude histograms.
To determine quantal event parameters: mean peak current (<q>), coefficient of variation (CVq), number of release sites (NS), and release probability (PR).
To investigate the underlying release mechanisms and factors contributing to amplitude variability.

Main Methods:

Analysis of unitary EPSC amplitude histograms from MF-CA3 synapses.
Fitting histograms using models with binomial, nonuniform, or nonstationary release statistics.
Quantifying quantal event properties and number of release sites.

Main Results:

Quantal events involve the opening of 15-65 AMPA-type glutamate receptor (GluR) channels.
Quantal event amplitude variability (CVq) is between 25-30%.
The number of release sites per MF bouton ranges from 8-21, aligning with morphological data.
Postsynaptic factors may significantly contribute to unitary EPSC amplitude fluctuations.

Conclusions:

MF-CA3 synapses likely operate with independent release sites, each contributing a quantal event.
The interpretation of multipeak EPSC amplitude distributions solely based on release probability may be an oversimplification.
Postsynaptic mechanisms play a substantial role in the variability of unitary EPSC amplitudes at MF-CA3 synapses.