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Dynamic changes in phrenic motor output following high cervical hemisection in the decerebrate rat
Journal article   Peer reviewed

Dynamic changes in phrenic motor output following high cervical hemisection in the decerebrate rat

Michael George Zaki Ghali and Vitaliy Marchenko
Experimental neurology, v 271, pp 379-389
01 Sep 2015
DOI: https://doi.org/10.1016/j.expneurol.2015.06.002
PMID: 26056711
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

Life Sciences & Biomedicine Neurosciences Neurosciences & Neurology Science & Technology
Hemisection of the spinal cord at C-2 eliminates ipsilateral descending drive to the phrenic nucleus and causes hemidiaphragmatic paralysis in rats. Phrenic nerve (PhN) or diaphragmatic activity ipsilateral to hemisection can occasionally be induced acutely following hemisection by respiratory stressors (i.e., hypercapnia, asphyxia, contralateral phrenicotomy) and becomes spontaneously active days-to-weeks later. These investigations, however, are potentially confounded by the use of anesthesia, which may suppress spontaneously-active crossed phrenic pathways. Experiments were performed on vecuronium-paralyzed, unanesthetized, decerebrate adult male rats and whole PhN activity recorded continuously before, during, and after high cervical hemisection at the C-1 spinal level. Crossed phrenic activity recovered spontaneously over minutes-to-hours with maximal recovery of 11.8 +/- 3.1% (m +/- SE) in the PhN ipsilateral to hemisection. Additionally, there was a significant increase in PhN activity contralateral to hemisection of 221.0 +/- 40.4% (m +/- SE); since animals were artificially-ventilated, these changes likely represent an increase in central respiratory drive. These results underscore the state-dependence of crossed bulbophrenic projections and suggest that unanesthetized models may be more sensitive in detecting acute recovery of respiratory output following spinal cord injury (SCI). Additionally, our results may suggest an important role for a group of C-1-C-2 neurons exhibiting respiratory-related activity, spared by the higher level of hemisection. These units may function as relays of polysynaptic bulbophrenic pathways and/or provide excitatory drive to phrenic motoneurons. Our findings provide a new model for investigating acute respiratory recovery following cervical SCI, the high C-1-hemisected unanesthetized decerebrate rat and suggest a centrally-mediated increase in central respiratory drive in response to high cervical SCI. (C) 2015 Elsevier Inc. All rights reserved.

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