Neuron
Volume 77, Issue 1, 9 January 2013, Pages 129-140
Journal home page for Neuron

Article
Fast Silencing Reveals a Lost Role for Reciprocal Inhibition in Locomotion

https://doi.org/10.1016/j.neuron.2012.10.040Get rights and content
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Summary

Alternating contractions of antagonistic muscle groups during locomotion are generated by spinal “half-center” networks coupled in antiphase by reciprocal inhibition. It is widely thought that reciprocal inhibition only coordinates the activity of these muscles. We have devised two methods to rapidly and selectively silence neurons on just one side of Xenopus tadpole spinal cord and hindbrain, which generate swimming rhythms. Silencing activity on one side led to rapid cessation of activity on the other side. Analyses reveal that this resulted from the depression of reciprocal inhibition connecting the two sides. Although critical neurons in intact tadpoles are capable of pacemaker firing individually, an effect that could support motor rhythms without inhibition, the swimming network itself requires ∼23 min to regain rhythmic activity after blocking inhibition pharmacologically, implying some homeostatic changes. We conclude therefore that reciprocal inhibition is critical for the generation of normal locomotor rhythm.

Highlights

► Silencing activity on one side stops fictive swimming ► Silencing activity on one side depresses reciprocal inhibition ► Motor rhythms resume ∼23 min after pharmacological block of inhibition ► Reciprocal inhibition is essential for maintaining swimming

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Present address: School of Psychology and Neuroscience, University of St. Andrews, Bute Building, St. Andrews KY16 9TS, UK