Node of Ranvier length as a potential regulator of myelinated axon conduction speed

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Abstract

Myelination speeds conduction of the nerve impulse, enhancing cognitive power. Changes of white matter structure contribute to learning, and are often assumed to reflect an altered number of myelin wraps. We now show that, in rat optic nerve and cerebral cortical axons, the node of Ranvier length varies over a 4.4-fold and 8.7-fold range respectively and that variation of the node length is much less along axons than between axons. Modelling predicts that these node length differences will alter conduction speed by ~20%, similar to the changes produced by altering the number of myelin wraps or the internode length. For a given change of conduction speed, the membrane area change needed at the node is >270-fold less than that needed in the myelin sheath. Thus, axon-specific adjustment of node of Ranvier length is potentially an energy-efficient and rapid mechanism for tuning the arrival time of information in the CNS.<br /><strong> </strong>

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I Lorena Arancibia-Carcamo

Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Marc C Ford

Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-0472-2652
Lee Cossell

Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom

Competing interests
The authors declare that no competing interests exist.
Kinji Ishida

The Center for Electron Microscopy and Bio-Imaging Research, Iwate Medical University, Morioka, Japan

Competing interests
The authors declare that no competing interests exist.
Koujiro Tohyama

The Center for Electron Microscopy and Bio-Imaging Research, Iwate Medical University, Morioka, Japan

For correspondence
tohyama@coral.plala.or.jp

Competing interests
The authors declare that no competing interests exist.
David Attwell

Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom

For correspondence
d.attwell@ucl.ac.uk

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-3618-0843

Funding

Wellcome (099222/Z/12/Z)

I Lorena Arancibia-Carcamo
Lee Cossell
David Attwell

European Commission (623714 AxonGliaPlasticity)

Marc C Ford

Japan Society for the Promotion of Science London (24650181)

Kinji Ishida
Koujiro Tohyama

Japan Society for the Promotion of Science London (25245069)

Kinji Ishida
Koujiro Tohyama

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: This work was performed in accordance with the United Kingdom Animals (Scientific Procedures) Act (1986) and subsequent amendments, under UK Home Office licence (PPL 70/7299) and the electrom microscopy part of the work was approved by the Ethical Committee of Iwate Medical University.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.