Premium
Phrenic motor output and ventilation after graded unilateral cervical spinal cord injury (SCI)
Author(s) -
Doperalski Nicholas J,
Fuller David D
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1212
Subject(s) - medicine , spinal cord , white matter , anesthesia , hypercapnia , spinal cord injury , ventilation (architecture) , tidal volume , respiratory system , anatomy , magnetic resonance imaging , mechanical engineering , psychiatry , engineering , radiology
Histological examination of intended C2 spinal hemisection (C2HS) occasionally reveals healthy white matter in the ipsilateral ventral spinal cord. As a portion of bulbospinal inputs to phrenic motoneurons travel in this region (Lipski et al. Brain Res. 640:171–84, 1994), this tissue sparing could influence respiratory recovery. We sought to determine if ventral white matter sparing produced quantifiable differences (vs. complete C2HS) in breathing. Ventilation (awake rats) and phrenic activity (anesthetized rats) were quantified 4 wks post‐SCI and in uninjured rats (N=7). Tissue sparing was quantified as the ratio of ipsilateral:contralateral (ip:con) ventral white matter area at C2. Hemisection was classified as complete (ip:con = 0, N=7), mild sparing along the spinal midline (ip:con = 0.12 and 0.18, N=2), or moderate sparing (ip:con = 0.33 and 0.36, N=2). During normoxia, SCI rats had reduced inspiratory tidal volume (VT) vs. uninjured rats and breathing was similar across SCI groups. During hypercapnia (7% CO2), VT in the mild sparing rats was similar to complete C2HS rats, but VT in moderate sparing rats was similar to uninjured animals. Normoxic phrenic burst amplitude recorded ipsilateral to SCI (iPhr) was similarly attenuated in all SCI rats. During hypoxia (14% O2), iPhr (% contralateral burst) in moderate sparing rats was outside the C2HS 95% confidence interval, whereas values from the mild sparing rats were within this range. We suggest that neural pathways in the most medial portions of the C2 ventral white matter have little impact on breathing after SCI; pathways located slightly more lateral are important during states of increased respiratory drive. Supported by the Christopher Reeve Foundation and the American Paraplegia Society.