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Electrophysiological and Morphological Characterization of Neuronal Microcircuits in Acute Brain Slices Using Paired Patch-Clamp Recordings
Published on: January 10, 2015
Quantal analysis reveals a functional correlation between presynaptic and postsynaptic efficacy in excitatory
Neil R Hardingham1, Jenny C A Read, Andrew J Trevelyan
1The University Laboratory of Physiology, Oxford University, Oxford, OX1 3PT, United Kingdom. hardinghamnr@cardiff.ac.uk
Summary
Synaptic connections in the rat visual cortex show coordinated presynaptic and postsynaptic strength scaling. This functional correlation influences the efficacy of neuronal communication, impacting synaptic transmission.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Computational Neuroscience
Background:
- Structural correlations between presynaptic and postsynaptic elements are known at central synapses.
- The functional implications of these structural correlations at synapses remain largely unexplored.
Purpose of the Study:
- To investigate whether structural correlations at central synapses extend to functional properties.
- To determine the relationship between presynaptic release probability and postsynaptic quantal size in cortical neurons.
Main Methods:
- Electrophysiological recordings from synaptically coupled pyramidal neuron pairs in rat visual cortex.
- Analysis of excitatory postsynaptic potentials (EPSPs) including amplitude and rise time.
- Quantal analysis using binomial statistics to estimate release probability (P(r)) and quantal size (Q).
- Anatomical reconstructions of a subset of connected neuronal pairs.
Main Results:
- EPSP amplitudes varied significantly (40 microV to 2.9 mV) with rise times suggesting basal dendritic localization.
- Over 30% of connections fit a binomial quantal model.
- Significant heterogeneity in P(r) and Q was observed between connections.
- A positive correlation was found between P(r) and Q across populations of connections for both L2/3 and L5 pyramidal neurons.
- Mean EPSP amplitude correlated with Q and P(r), but not N (number of release sites) for L2/3 to L2/3 connections.
Conclusions:
- Functional properties of cortical synapses, specifically release probability and quantal size, are positively correlated.
- Presynaptic and postsynaptic strengths are dependently scaled during the development of cortical connections.
- The overall efficacy of a cortical connection is determined by the coordinated scaling of presynaptic and postsynaptic strengths.
