Advanced Age Impairs the Neuromuscular Control of Peak Inspiratory Performance in Mice

Abstract

Respiratory muscle wasting is known to occur in ageing adults resulting in a decreased capacity for force production and an associated reduction in high-threshold respiratory performance. Dysfunction of the respiratory musculature in this manner may contribute to an increased susceptibility to respiratory complications frequently observed in older populations. The objective of the current study was to characterise the respiratory phenotype during advanced age to assess the impact of sarcopenia on the neuromuscular control of respiratory performance. Male wild type (BL10) mice were studied at 6-months and 24-months, representing young and old age cohorts, respectively. In anaesthetised animals, inspiratory pressure and contemporaneous obligatory and accessory respiratory muscle electromyography (EMG) activities were measured during baseline and sustained tracheal occlusion (n = 9 young; n = 8 old). Diaphragm muscle contractile performance was assessed ex-vivo via tissue bath preparations (n = 8 young; n = 8 old). Furthermore, diaphragm and limb muscle tissues were harvested and snap frozen for subsequent structural and molecular analyses which will assess potential differences in cross-sectional area and relative fibre type composition. Peak inspiratory pressure was significantly reduced in 24-month-old compared to 6-month-old mice (P < 0.0001). Associated EMG activity was significantly lower (P < 0.05) in obligatory (external intercostal; parasternal) and accessory (cleidomastoid; scalene; trapezius; sternomastoid; sternohyoid) muscles of breathing in the old group compared to the young. Diaphragm EMG amplitude was not different between the groups. No differences were observed in the force-generating capacity of the diaphragm between young and old cohorts. Our preliminary results suggest an impairment in the neuromuscular control of the respiratory system during peak performance which apparently precedes the age-related decline in diaphragm muscle force generating capacity. Our further histological and molecular analyses will provide additional insight into the nature of this respiratory phenotype in advanced age. This work was funded by the Department of Physiology, UCC. B.T. Murphy is funded by an Irish Research Council Doctoral Scholarship. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.