Figure 2.

In vivo airway resistance responses to contractile ligands are decreased in βAR^–/– mice. Intubated mice were administered aerosolized solutions of PBS, methacholine (MCh) (80 mg/ml), serotonin (20 mg/ml), and methacholine with 1.0 mg/ml isoproterenol (MCh + Iso) in PBS, and then airway resistance was measured after each administration. Baseline resistance was not different between wild-type and βAR^–/– mice (see text), but the latter had virtually no contractile responses to methacholine or serotonin (P < 0.001 by ANOVA). Results are from four to six mice of each genotype. *Not different (P > 0.05) from baseline resistance.