In:
Journal of Applied Physiology, American Physiological Society, Vol. 112, No. 1 ( 2012-01-01), p. 96-105
Abstract:
Spinal cord hemisection at C2 (C2HS) severs bulbospinal inputs to ipsilateral phrenic motoneurons causing transient hemidiaphragm paralysis. The spontaneous crossed-phrenic phenomenon (sCPP) describes the spontaneous recovery of ipsilateral phrenic bursting following C2HS. We reasoned that the immediate (next breath) changes in tidal volume (V T ) induced by ipsilateral phrenicotomy during spontaneous breathing would provide a quantitative measure of the contribution of the sCPP to postinjury V T . Using this approach, we tested the hypothesis that the sCPP makes more substantial contributions to V T when respiratory drive is increased. Pneumotachography was used to measure V T in anesthetized, spontaneously breathing adult male rats at intervals following C2HS. A progressive increase in V T (ml/breath) occurred over an 8 wk period following C2HS during both poikilocapnic baseline breathing and hypercapnic respiratory challenge (7% inspired CO 2 ). The sCPP did not impact baseline breathing at 1–3 days postinjury since V T was unchanged after ipsilateral phrenicotomy. However, by 2 wk post-C2HS, baseline phrenicotomy caused a 16 ± 2% decline in V T ; a comparable 16 ± 4% decline occurred at 8 wk. Contrary to our hypothesis, the phrenicotomy-induced declines in V T (%) during hypercapnic respiratory stimulation did not differ from the baseline response at any postinjury time point (all P 〉 0.11). We conclude that by 2 wk post-C2HS the sCPP makes a meaningful contribution to V T that is similar across different levels of respiratory drive.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00690.2011
Language:
English
Publisher:
American Physiological Society
Publication Date:
2012
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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