Chronic Intermittent Hypoxia and Respiratory Motor Plasticity after Cervical Spinal Cord Contusion

Abstract

Chronic intermittent hypoxia (CIH), characterized by > 100 hypoxic episodes per day, is a hallmark of moderate sleep apnea, a condition highly prevalent in individuals with spinal cord injury. Both 1 day (Huxtable et al., 2013) and 7 days (Gonzalez‐Rothi, in preparation) of CIH (15 episodes/hour; 8 hours/day) abolish phrenic motor plasticity in intact rats due to neural inflammation. Although a milder CIH protocol (40 episodes/day) enhances phrenic activity in acutely injured rats (Fuller et al., 2003), the effects of CIH protocols that more closely approximate moderate sleep apnea have not been explored in animal models of chronic spinal injury. Thus, we are evaluating the impact of moderate CIH (2 min hypoxic episodes, 2 min intervals; 8 hrs; single day) on phrenic nerve activity and the capacity to elicit phrenic motor plasticity in rats with chronic C3/4 midline contusion injury (12 wks). Neurophysiology experiments conducted one day post‐CIH are ongoing and include assessments of: 1) phrenic nerve activity during baseline and maximal chemoreflex activation; and 2) moderate AIH‐induced phrenic long‐term facilitation (pLTF). Preliminary analysis suggests reduced pLTF in contused rats exposed to CIH. These experiments are the first to explore the effects of CIH on respiratory outcomes following chronic spinal contusion. Further experiments are required to explore the impact of: 1) prolonged CIH exposures on breathing ability after chronic cervical contusion; and 2) whether reducing neural inflammation will enhance phrenic plasticity and translate into improved functional recovery following chronic spinal cord injury.Support or Funding InformationThe Department of Defense: SCI160123 (EGR); and the National Institutes of Health: K12 HDO55929 (EGR)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.