Mild Acute Intermittent Hypoxia Improves Respiratory Function in Unanesthetized Rats With Midcervical Contusion.
Mild intermittent hypoxia has been considered a potential approach to induce respiratory neuroplasticity.



The purpose of the present study was to investigate whether mild acute intermittent hypoxia can improve breathing function in a clinically relevant spinal cord injury animal model.



Adult male rats received laminectomy or unilateral contusion at the C3-C4 spinal cord using a MASCIS Impactor (height: 6.25 or 12.5 mm). At 4 weeks postinjury, the breathing patterns of unanesthetized rats were measured by whole body plethysmography before, during and after 10 episodes of 5 minutes of hypoxia (10% O2, 4% CO2, balance N2) with 5 minutes of normoxia intervals.



The results demonstrated that cervical contusion resulted in reduction in breathing capacity and number of phrenic motoneurons. Acute hypoxia induced significant increases in frequency and tidal volume in sham surgery and contused animals. In addition, there was a progressive decline in the magnitude of hypoxic ventilatory response during intermittent hypoxia. Further, the tidal volume was significantly enhanced in contused but not sham surgery rats at 15 and 30 minutes postintermittent hypoxia, suggesting intermittent hypoxia can bring about long-term facilitation of tidal volume following cervical spinal contusion.



These results suggest that mild acute intermittent hypoxia can elicit differential forms of respiratory plasticity in sham surgery versus contused animals, and may be a promising neurorehabilitation approach to improve respiratory function after cervical spinal cord injury.
1 Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.|2 Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan.|3 Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, Taiwan.|4 Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University and Academia Sinica, Taiwan.|5 Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
Kun-Ze
KZ
Lee
1 Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.
Shu-Chi
SC
Chiang
1 Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.
Yu-Jie
YJ
Li
D000818:Animals; D066193:Cervical Cord / Q000473:pathology / Q000503:physiopathology; D002574:Cervical Vertebrae; D004195:Disease Models, Animal; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009046:Motor Neurons / Q000473:pathology / Q000502:physiology; D000066530:Neurological Rehabilitation; D009584:Nitrogen / Q000008:administration & dosage; D010100:Oxygen / Q000008:administration & dosage; D010791:Phrenic Nerve / Q000473:pathology / Q000503:physiopathology; D010993:Plethysmography, Whole Body; D017207:Rats, Sprague-Dawley; D012119:Respiration; D013119:Spinal Cord Injuries / Q000473:pathology / Q000503:physiopathology* / Q000534:rehabilitation*; D013990:Tidal Volume
D009584:Nitrogen; D010100:Oxygen
cervical spinal contusion; intermittent hypoxia; ventilation