Fig. 4.

Airways and bronchial rings of Gaa^−/− mice have an attenuated response to albuterol. A–C: after MCh dosage response, R-albuterol was nebulized and measurement cycle was taken, and then an additional measurement was taken postalbuterol. A and B: Gaa^−/− mice have a decreased response to albuterol in vivo compared with WT controls as evidenced by a lack of response in overall pulmonary resistance (R_rs; A) and central airway resistance (R_n; B). WT (n = 4) and Gaa^−/− (n = 5) mice. C: tissue resistance (G) did not respond to R-albuterol in WT or Gaa^−/− animals. D and E: ex vivo Gaa^−/− bronchial rings have a blunted response to the bronchodilator effects of R-albuterol compared with WT bronchial rings. D: representative tracing of bronchial ring force as a response to R-albuterol administration following MCh-induced contraction. E: summary data of R-albuterol inhibitory effects on MCh-induced tone as percent relaxation. The values were normalized to the max effect of MCh on smooth muscle tone in both WT (n = 6) and Gaa^−/− (n = 7) mice. *P ≤ 0.05, pair-wise comparison. #P ≤ 0.05, baseline comparison.