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Functional plasticity in the respiratory drive to thoracic motoneurons in the segment above a chronic lateral spinal cord lesion

Ford, T. W.; Anissimova, N. P.; Meehan, C. F.; Kirkwood, P. A.

Authors

T. W. Ford timothy.ford@nottingham.ac.uk

N. P. Anissimova

C. F. Meehan

P. A. Kirkwood peter.kirkwood@ucl.ac.uk



Abstract

A previous neurophysiological investigation demonstrated an increase in functional projections of expiratory bulbospinal neurons (EBSNs) in the segment above a chronic lateral thoracic spinal cord lesion which severed their axons. We have now investigated how this plasticity might be manifested in thoracic motoneurons, by measuring their respiratory drive and the connections to them from individual EBSNs. In anesthetized cats, simultaneous recordings were made intracellularly from motoneurons in the segment above a left-side chronic (16 week) lesion of the spinal cord in the rostral part of T8, T9 or T10 and extracellularly from EBSNs in the right caudal medulla, antidromically excited from just above the lesion, but not from below. Spike-triggered averaging was used to measure the connections between pairs of EBSNs and motoneurons. Connections were found to have a very similar distribution to normal and were, if anything (non-significantly), weaker than normal, being present for 42/158 pairs, vs. 55/154 pairs in controls. The expiratory drive in expiratory motoneurons appeared stronger than in controls, but again not significantly so. Thus we conclude that new connections made by the EBSNs following these lesions were made to neurons other than alpha-motoneurons. However, a previously unidentified form of functional plasticity was seen, in that there was a significant increase in the excitation of motoneurons during post-inspiration, being manifest either in increased incidence of expiratory-decrementing respiratory drive potentials, or in an increased amplitude of the post-inspiratory depolarizing phase in inspiratory motoneurons. We suggest that this component arose from spinal cord interneurons.

Journal Article Type Article
Publication Date 2016-01
Journal Journal of Neurophysiology
Print ISSN 0022-3077
Electronic ISSN 1522-1598
Publisher American Physiological Society
Peer Reviewed Not Peer Reviewed
Volume 115
Issue 1
Pages 554-567
APA6 Citation Ford, T. W., Anissimova, N. P., Meehan, C. F., & Kirkwood, P. A. (2016). Functional plasticity in the respiratory drive to thoracic motoneurons in the segment above a chronic lateral spinal cord lesion. Journal of Neurophysiology, 115(1), 554-567. https://doi.org/10.1152/jn.00614.2015
DOI https://doi.org/10.1152/jn.00614.2015
Keywords Spinal cord injury, Thoracic motoneurons, Respiratory drive, Plasticity
Publisher URL https://journals.physiology.org/doi/full/10.1152/jn.00614.2015#
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0





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