It takes two to tango: M-current swings with the persistent sodium current to set the speed of locomotion.

Link to bioRxiv paper:
http://biorxiv.org/cgi/content/short/2020.04.24.059311v1?rss=1
Authors: Verneuil, J., Brocard, C., Villard, L., Peyronnet-Roux, J., Brocard, F.
Abstract:
The central pattern generator (CPG) for locomotion is set of pacemaker neurons endowed with inherent bursting driven by the persistent sodium current ( I NaP ). How they proceed to regulate the locomotor rhythm remained unknown. Here, in neonatal rodents, we identified a persistent potassium current, critical in regulating pacemakers and locomotion speed. This current recapitulates features of the M-current ( I M ); a subthreshold non-inactivating outward current blocked by XE991 and enhanced by ICA73. Immunostaining and mutant mice highlight an important role of axonal Kv7.2 channels in mediating I M . Pharmacological modulation of I M regulates the emergence and the frequency regime of both pacemaker and CPG activities, and controls the speed of locomotion. Computational models captured these results and show howed an interplay between I M and I NaP that endows the locomotor CPG with rhythmogenic properties. Overall, this study provides fundamental insights into how I M and I NaP work in tandem to set the speed of locomotion.
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