Synaptic up-scaling preserves motor circuit output after chronic, natural inactivity

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Abstract

Neural systems use homeostatic plasticity to maintain normal brain functions and to prevent abnormal activity. Surprisingly, homeostatic mechanisms that regulate circuit output have mainly been demonstrated during artificial and/or pathological perturbations. Natural, physiological scenarios that activate these stabilizing mechanisms in neural networks of mature animals remain elusive. To establish the extent to which a naturally inactive circuit engages mechanisms of homeostatic plasticity, we utilized the respiratory motor circuit in bullfrogs that normally remains inactive for several months during the winter. We found that inactive respiratory motoneurons exhibit a classic form of homeostatic plasticity, up-scaling of AMPA-glutamate receptors. Up-scaling increased the synaptic strength of respiratory motoneurons and acted to boost motor amplitude from the respiratory network following months of inactivity. Our results show that synaptic scaling sustains strength of the respiratory motor output following months of inactivity, thereby supporting a major neuroscience hypothesis in a normal context for an adult animal.

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Joseph M Santin

Division of Biological Sciences, University of Missouri, Columbia, United States

For correspondence
santinj@missouri.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-1308-623X
Mauricio Vallejo

Department of Biological Sciences, Wright State University, Dayton, United States

Competing interests
The authors declare that no competing interests exist.
Lynn K Hartzler

Department of Biological Sciences, Wright State University, Dayton, United States

Competing interests
The authors declare that no competing interests exist.

Funding

Wright State University Department of Biological Sciences: Biology Award for Research Excellence

Joseph M Santin

Wright State University Biomedical Sciences PhD Program

Joseph M Santin

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

Ethics

Animal experimentation: Experiments were approved by the Wright State University Institutional Animal Care and Use Committee (protocol number 1047).

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.