Rosiglitazone (RGZ), but not β-adrenoceptor agonists, elicits full relaxation of mouse small airways in lung slices. Airways in lung slices were precontracted with 300 nM methacholine (MCh) to achieve ∼ 70% of the maximum MCh response before perfusion with increasing concentrations of RGZ, albuterol (ALB), or isoproterenol (ISO). (A) Representative phase-contrast images of the last frame of each 5-minute perfusion period and frame-by-frame analysis (0.5 Hz) show changes in lumen area with time in the presence of MCh and RGZ. Responses (mean ± SEM) to precontraction with MCh (B) before relaxation with RGZ (n = 4), ALB (n = 8), and ISO (n = 7) (C) are expressed as % initial airway lumen area and % relaxation of the submaximal MCh precontraction, respectively.