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C-bouton components on rat extensor digitorum longus motoneurons are resistant to chronic functional overload

Kissane, RWP; Ghaffari-Rafi, A; Tickle, PG; Chakrabarty, S; Egginton, S; Brownstone, RM; Smith, CC; (2021) C-bouton components on rat extensor digitorum longus motoneurons are resistant to chronic functional overload. Journal of Anatomy 10.1111/joa.13439. (In press). Green open access

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Abstract

Mammalian motor systems adapt to the demands of their environment. For example, muscle fibre types change in response to increased load or endurance demands. However, for adaptations to be effective, motoneurons must adapt such that their properties match those of the innervated muscle fibres. We used a rat model of chronic functional overload to assess adaptations to both motoneuron size and a key modulatory synapse responsible for amplification of motor output, C‐boutons. Overload of extensor digitorum longus (EDL) muscles was induced by removal of their synergists, tibialis anterior muscles. Following 21 days survival, EDL muscles showed an increase in fatigue resistance and a decrease in force output, indicating a shift to a slower phenotype. These changes were reflected by a decrease in motoneuron size. However, C‐bouton complexes remained largely unaffected by overload. The C‐boutons themselves, quantified by expression of vesicular acetylcholine transporter, were similar in size and density in the control and overload conditions. Expression of the post‐synaptic voltage‐gated potassium channel (KV2.1) was also unchanged. Small conductance calcium‐activated potassium channels (SK3) were expressed in most EDL motoneurons, despite this being an almost exclusively fast motor pool. Overload induced a decrease in the proportion of SK3+ cells, however, there was no change in density or size of clusters. We propose that reductions in motoneuron size may promote early recruitment of EDL motoneurons, but that C‐bouton plasticity is not necessary to increase the force output required in response to muscle overload.

Type: Article
Title: C-bouton components on rat extensor digitorum longus motoneurons are resistant to chronic functional overload
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/joa.13439
Publisher version: https://doi.org/10.1111/joa.13439
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Keywords: Science & Technology, Life Sciences & Biomedicine, Anatomy & Morphology, C&#8208, bouton, K(V)2, 1, overload, plasticity, SK3, spinal cord
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Department of Neuromuscular Diseases
URI: https://discovery.ucl.ac.uk/id/eprint/10127701
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