Ipsilateral inspiratory intercostal muscle activity after C2 spinal cord hemisection in rats

Abstract

Background: Upper cervical spinal cord hemisection causes paralysis of the ipsilateral hemidiaphragm; however, the effect of C2 hemisection on the function of the intercostal muscles is not clear. We hypothesized that C2 hemisection would eliminate inspiratory intercostal activity ipsilateral to the injury and that some activity would return in a time-dependent manner. Methods: Female Sprague Dawley rats were anesthetized with urethane and inspiratory intercostal electromyogram (EMG) activity was recorded in control rats, acutely injured C2 hemisected rats, and at 1 and 16 weeks post C2 hemisection. Results: Bilateral recordings of intercostal EMG activity showed that inspiratory activity was reduced immediately after injury and increased over time. EMG activity was observed first in rostral spaces followed by recovery occurring in caudal spaces. Theophylline increased respiratory drive and increased intercostal activity, inducing activity that was previously absent. Conclusion: These results suggest that there are crossed, initially latent, respiratory connections to neurons innervating the intercostal muscles similar to those innervating phrenic motor neurons.

Novel regenerative drug, SPG302 promotes functional recovery of diaphragm muscle activity after cervical spinal cord injury

“…After C 2 SH, up to 50% of DIAm force‐generating capacity may be lost, which can certainly affect P di . Furthermore, there may be deficits in the activation of chest wall muscles following C 2 SH that alter chest wall compliance (Beth Zimmer et al., 2015; Denton & McKinlay, 2009), which may also affect P di . We hypothesise that 14‐day treatment with SPG302 will improve recovery of inspiratory‐related DIAm EMG and P di following C 2 SH.…”

Mid-cervical spinal cord contusion causes robust deficits in respiratory parameters and pattern variability

“…These data confirm the findings of previous studies (Wen and Lee, 2017). The recovery in activity of the ipsilateral external intercostals is more rapid then the seven-fourteen day time-lag shown following C2 hemisection (Beth Zimmer et al, 2015; Dougherty et al, 2012; Navarrete-Opazo et al, 2015) and is likely mediated through propriospinal interneurons which upregulate following trauma (Lane et al, 2008).…”

Reorganization of Respiratory Descending Pathways following Cervical Spinal Partial Section Investigated by Transcranial Magnetic Stimulation in the Rat

“…The implications of other respiratory related muscles (i.e. intercostals and abdominals, Fig 5B and 5C ) for maintaining a certain respiratory gazes exchange homeostasis and for compensating for the maintenance of respiratory function following a chronic C2 hemisection have already been demonstrated [ 36 , 37 ]. Interestingly, the injury size contributes to the spontaneous functional recovery as well as to the respiratory deficit.…”