['Supplemental O', 'Newborn mouse litters were randomized to 85% O', 'Hyperoxic mice had increased airway reactivity at baseline and following methacholine challenge in vivo (8 and 12 weeks); isolated tracheal rings had a significantly higher constriction response to methacholine in vitro compared to RA group. Inflammatory markers were higher at 2 weeks (MCP-1, IL-12, INF-γ) and at 15 weeks (LTB'] Does neonatal hyperoxia increase airway reactivity and inflammation in adult mice?