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Respiratory behavior following chronic C2 hemisection (C2HS) in awake rats
Author(s) -
Doperalski Nicholas J,
Morrison Sandy A,
Bolser Don C,
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.a1211-c
Subject(s) - tidal volume , hypercapnia , ventilation (architecture) , medicine , anesthesia , respiratory rate , respiratory system , respiratory minute volume , respiration , respiratory frequency , plethysmograph , expiration , cardiology , heart rate , anatomy , mechanical engineering , blood pressure , engineering
Phrenic motor plasticity and recovery after C2HS has been widely studied in anesthetized animals. However, the impact of C2HS on respiratory behavior in awake animals has not been thoroughly characterized. Barometric plethysmography was used to study breathing in 4 groups of awake, unrestrained rats: uninjured (N=81), and 2 (N=10), 4 (N=10), or 8 weeks (N=9) post‐C2HS. The following parameters were quantified: inspiratory tidal volume (VT), frequency (F) and minute ventilation (VE), inspiratory (TI) and expiratory duration (TE), peak inspiratory (PIF) and expiratory airflow (PEF), mean inspiratory airflow (VT/TI), the ratio of VE to metabolic rate (VE/VCO2), and the frequency and amplitude of spontaneous augmented breaths (ABs). During quiet breathing (21% O2, balance N2), VE and VE/VCO2 were unaffected after C2HS. However, VT, TI, TE, VT/TI, PIF, PEF and AB amplitude were diminished, and F was elevated (p<0.05 vs. uninjured). Over 2–8 weeks post‐C2HS, the breathing pattern shifted towards that of uninjured rats. Specifically, VT, TI, TE, and PIF all increased, and F decreased (p<0.05). During hypercapnia (7% CO2, balance O2), VE, VT, VT/TI, PIF, PEF, and AB amplitude were all reduced in the C2HS rats (p<0.05 vs. uninjured). In contrast, hypercapnic F, TI and TE were unaffected by C2HS. Over the period of 2–8 weeks post‐C2HS, VE, VT, PIF, PEF and VT/TI all increased (p<0.05). We conclude that rats maintain adequate ventilation after C2HS during quiet breathing, but are unable to do so when respiratory drive is increased. Spontaneous improvements in VT and PIF may reflect time‐dependent recruitment of crossed phrenic pathways. Supported by the Christopher Reeve Foundation and the American Paraplegia Society.