Synaptic mechanisms underlying modulation of locomotor-related motoneuron output by premotor cholinergic interneurons
- University of St Andrews, United Kingdom
- Biomedical Research Foundation of the Academy of Athens, Greece
Abstract
Spinal motor networks are formed by diverse populations of interneurons that set the strength and rhythmicity of behaviors such as locomotion. A small cluster of cholinergic interneurons, expressing the transcription factor Pitx2, modulates the intensity of muscle activation via 'C-bouton' inputs to motoneurons. However, the synaptic mechanisms underlying this neuromodulation remain unclear. Here, we confirm in mice that Pitx2+ interneurons are active during fictive locomotion and that their chemogenetic inhibition reduces the amplitude of motor output. Furthermore, after genetic ablation of cholinergic Pitx2+ interneurons, M2 receptor-dependent regulation of the intensity of locomotor output is lost. Conversely, chemogenetic stimulation of Pitx2+ interneurons leads to activation of M2 receptors on motoneurons, regulation of Kv2.1 channels and greater motoneuron output due to an increase in the inter-spike afterhyperpolarization and a reduction in spike half-width. Our findings elucidate synaptic mechanisms by which cholinergic spinal interneurons modulate the final common pathway for motor output.
Data availability
All of the data presented in this study are included in the manuscript and supporting files
Article and author information
Author details
Matthew James Broadhead
Funding
Alfred Dunhil Links Foundation
- Filipe Nascimento
Biotechnology and Biological Sciences Research Council (BB/M021793/1)
- Matthew James Broadhead
- Gareth Miles
Foundation Sante
- Eirini Tsape
- Laskaro Zagoraiou
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All the procedures performed on animals were conducted in accordance with the UK Animals (Scientific Procedures) Act 1986 and were approved by the University of St Andrews Animal Welfare Ethics Committee. Experiments on animals performed in the Biomedical Research Foundation of the Academy of Athens were approved by the competent veterinary service of the Prefecture of Athens, Greece in accordance with the existing legal framework. The facility is registered as a 'breeding' and 'user' establishment by the Veterinary Service of the Prefecture of Athens according to the Presidential Decree 56/2013 in harmonization with the European Directive 2010/63/EU for the protection of animals used for scientific purposes.
Copyright
© 2020, Nascimento et al.
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.
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Synaptic mechanisms underlying modulation of locomotor-related motoneuron output by premotor cholinergic interneurons
eLife 9:e54170.
https://doi.org/10.7554/eLife.54170
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