Superresolution imaging reveals activity-dependent plasticity of axon morphology linked to changes in action potential conduction velocity

Ronan Chéreau, G. Ezequiel Saraceno, Julie Angibaud, Daniel Cattaert, U. Valentin Nägerl
Proc Natl Acad Sci USA. 2017-01-23; 114(6): 1401-1406
DOI: 10.1073/pnas.1607541114

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1. Proc Natl Acad Sci U S A. 2017 Feb 7;114(6):1401-1406. doi:
10.1073/pnas.1607541114. Epub 2017 Jan 23.

Superresolution imaging reveals activity-dependent plasticity of axon morphology
linked to changes in action potential conduction velocity.

Chéreau R(1)(2), Saraceno GE(1)(2), Angibaud J(1)(2), Cattaert D(1)(3), Nägerl
UV(4)(2).

Author information:
(1)Department of Life and Health Sciences, Université de Bordeaux, 33077
Bordeaux, France.
(2)Interdisciplinary Institute for Neuroscience, UMR 5297, Centre National de la
Recherche Scientifique, 33077 Bordeaux, France.
(3)Institut de Neurosciences Cognitives et Intégratives d’Aquitaine, UMR 5287,
Centre National de Recherche Scientifique, 33077 Bordeaux, France.
(4)Department of Life and Health Sciences, Université de Bordeaux, 33077
Bordeaux, France; *protected email*.

Axons convey information to nearby and distant cells, and the time it takes for
action potentials (APs) to reach their targets governs the timing of information
transfer in neural circuits. In the unmyelinated axons of hippocampus, the
conduction speed of APs depends crucially on axon diameters, which vary widely.
However, it is not known whether axon diameters are dynamic and regulated by
activity-dependent mechanisms. Using time-lapse superresolution microscopy in
brain slices, we report that axons grow wider after high-frequency AP firing:
synaptic boutons undergo a rapid enlargement, which is mostly transient, whereas
axon shafts show a more delayed and progressive increase in diameter. Simulations
of AP propagation incorporating these morphological dynamics predicted
bidirectional effects on AP conduction speed. The predictions were confirmed by
electrophysiological experiments, revealing a phase of slowed down AP conduction,
which is linked to the transient enlargement of the synaptic boutons, followed by
a sustained increase in conduction speed that accompanies the axon shaft widening
induced by high-frequency AP firing. Taken together, our study outlines a
morphological plasticity mechanism for dynamically fine-tuning AP conduction
velocity, which potentially has wide implications for the temporal transfer of
information in the brain.

DOI: 10.1073/pnas.1607541114
PMCID: PMC5307438
PMID: 28115721 [Indexed for MEDLINE]

Conflict of interest statement: The authors declare no conflict of interest.


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