Journal
EXPERIMENTAL NEUROLOGY
Volume 287, Issue -, Pages 192-204Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.expneurol.2016.05.033
Keywords
Respiratory plasticity; Respiratory muscle; Amyotrophic lateral sclerosis; Motor neuron disease; Neurodegeneration; Ventilation failure; V2a neuron; Respiratory circuit
Categories
Funding
- ALS Association Starter Grant [T7EMDY]
- FightSMA!
- Gwendolyn Strong Foundation
- Cincinnati Children's Hospital Research Foundation Trustee Award
- CCHMC McLaurin Fund
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Inspiratory accessory respiratory muscles (ARMs) enhance ventilation when demands are high, such as during exercise and/or pathological conditions. Despite progressive degeneration of phrenic motor neurons innervating the diaphragm, amyotrophic lateral sclerosis (ALS) patients and rodent models are able to maintain ventilation at early stages of disease. In order to assess the contribution of ARMs to respiratory compensation in ALS, we examined the activity of ARMs and ventilation throughout disease progression in SOD1(G93A) ALS model mice at rest using a combination of electromyography and unrestrained whole body plethysmography. Increased ARM activity, accompanied by increased ventilation, is observed beginning at the onset of symptoms. However, ARM recruitment fails to occur at rest at late stages of disease, even though the same ARMs are used for other behaviors. Using a chemogenetic approach, we demonstrate that a glutamatergic class of neurons in the brainstem and spinal cord, the V2a class, is sufficient to drive increased ARM activity at rest in healthy mice. Additionally, we reveal pathology in the medial reticular formation of the brainstem of SOD1G93A mice using immunohistochemistry and confocal imaging. Both spinal and brainstem V2a neurons degenerate in ALS model mice, accompanied by regional activation of astrocytes and microglia. These results establish inspiratory ARM recruitment as one of the compensatory mechanisms that maintains breathing at early stages of disease and indicate that V2a neuron degeneration may contribute to ARM failure at late stages of disease. (C) 2016 Elsevier Inc. All rights reserved.
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