Phrenic motor neuron loss in aged rats

Matthew J. Fogarty, Tanya S. Omar, Wen Zhi Zhan, Carlos Bernardo Mantilla, Gary C Sieck

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Sarcopenia is the age-related reduction of muscle mass and specific force. In previous studies, we found that sarcopenia of the diaphragm muscle (DIAm) is evident by 24 mo of age in both rats and mice and is associated with selective atrophy of type IIx and IIb muscle fibers and a decrease in maximum specific force. These fiber type-specific effects of sarcopenia resemble those induced by DIAm denervation, leading us to hypothesize that sarcopenia is due to an age-related loss of phrenic motor neurons (PhMNs). To address this hypothesis, we determined the number of PhMNs in young (6 mo old) and old (24 mo old) Fischer 344 rats. Moreover, we determined age-related changes in the size of PhMNs, since larger PhMNs innervate type IIx and IIb DIAm fibers. The PhMN pool was retrogradely labeled and imaged with confocal microscopy to assess the number of PhMNs and the morphometry of PhMN soma and proximal dendrites. In older animals, there were 22% fewer PhMNs, a 19% decrease in somal surface area, and a 21% decrease in dendritic surface area compared with young Fischer 344 rats. The age-associated loss of PhMNs involved predominantly larger PhMNs. These results are consistent with an age-related denervation of larger, more fatigable DIAm motor units, which are required primarily for high-force airway clearance behaviors. NEW & NOTEWORTHY Diaphragm muscle sarcopenia in rodent models is well described in the literature; however, the relationship between sarcopenia and frank phrenic motor neuron (MN) loss is unexplored in these models. We quantify a 22% loss of phrenic MNs in old (24 mo) compared with young (6 mo) Fischer 344 rats. We also report reductions in phrenic MN somal and proximal dendritic morphology that relate to decreased MN heterogeneity in old compared with young Fischer 344 rats.

Original languageEnglish (US)
Pages (from-to)1852-1862
Number of pages11
JournalJournal of Neurophysiology
Volume119
Issue number5
DOIs
StatePublished - May 1 2018

Fingerprint

Motor Neurons
Diaphragm
Sarcopenia
Inbred F344 Rats
Muscles
Muscle Denervation
Carisoprodol
Denervation
Dendrites

Keywords

  • Neuro-motor control
  • Phrenic motor neuron
  • Sarcopenia

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

Fogarty, M. J., Omar, T. S., Zhan, W. Z., Mantilla, C. B., & Sieck, G. C. (2018). Phrenic motor neuron loss in aged rats. Journal of Neurophysiology, 119(5), 1852-1862. https://doi.org/10.1152/jn.00868.2017

Phrenic motor neuron loss in aged rats. / Fogarty, Matthew J.; Omar, Tanya S.; Zhan, Wen Zhi; Mantilla, Carlos Bernardo; Sieck, Gary C.

In: Journal of Neurophysiology, Vol. 119, No. 5, 01.05.2018, p. 1852-1862.

Research output: Contribution to journalArticle

Fogarty, MJ, Omar, TS, Zhan, WZ, Mantilla, CB & Sieck, GC 2018, 'Phrenic motor neuron loss in aged rats', Journal of Neurophysiology, vol. 119, no. 5, pp. 1852-1862. https://doi.org/10.1152/jn.00868.2017
Fogarty, Matthew J. ; Omar, Tanya S. ; Zhan, Wen Zhi ; Mantilla, Carlos Bernardo ; Sieck, Gary C. / Phrenic motor neuron loss in aged rats. In: Journal of Neurophysiology. 2018 ; Vol. 119, No. 5. pp. 1852-1862.
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