Respiratory Plasticity in Adult Rats after Exposure to Chronic Hyperoxia

Abstract

Neonatal rats reared in moderate hyperoxia (60% O2) from birth hypoventilate when acutely returned to room air (e.g., Bavis et al., Respir. Physiol. Neurobiol. 198: 1–12, 2014); this hypoventilation reflects reductions in both respiratory frequency and tidal volume. Since many forms of respiratory plasticity are specific to development, we questioned whether chronic hyperoxia would have similar effects on normoxic ventilation in adult rats. Adult Sprague‐Dawley rats (3–5 months old) were randomly assigned to Control (chronic 21% O2; n=11) or Hyperoxia (chronic 60% O2; n=10) treatment groups. Normoxic ventilation was measured by whole‐body plethysmography prior to exposure, after 4 and 14 days of exposure, and after 4 days of recovery in room air. Chronic hyperoxia altered minute ventilation in adult rats (Treatment × Day, P=0.002), but surprisingly this effect was not apparent during the hyperoxic exposure itself. Instead, Hyperoxia rats exhibited a modest increase in normoxic ventilation when measured during the recovery period (39±2 vs. 33±1 ml min−1 100g−1; P=0.003). Tidal volumes and respiratory frequencies were similar between groups before and during the chronic exposures, but Hyperoxia rats exhibited greater tidal volumes and respiratory frequencies during the recovery period (Treatment × Day, P=0.047 and 0.038, respectively). Neither metabolism nor blood gases were measured during these experiments, so it is unclear whether the increase in ventilation constitutes a true hyperventilation. We conclude that the effects of chronic hyperoxia on normoxic ventilation are age‐specific.Support or Funding InformationSupported by NIH grant P20 GM‐103423 (Maine INBRE).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.