Figure 2. Airways response to ipratropium aerosol with and without 10 mg/kg intravenous gallamine pretreatment as the percentage of control. The ipratropium aerosol was administered in doses of 0.01, 0.1, 1, and 10 mg/ml. The open squares represents the percentage change in airway lumenal area (mean +/- SEM) from control after each dose of ipratropium aerosol alone. The closed circles represents the percentage change in airway lumenal area from control (before gallamine administration) in the presence of intravenous gallamine pretreatment after ipratropium aerosol administration. Ipratropium aerosol alone significantly decreased airway lumenal area after the 0.01- and 0.1-mg/ml concentrations (*P < 0.01) and significantly increased lumenal area only after the 10-mg/ml concentration. Pretreatment with intravenous gallamine significantly constricted the airways (*P < 0.01). However, intravenous gallamine prevented the ipratropium-induced initial airway constriction. After intravenous gallamine pretreatment, ipratropium aerosol significantly dilated the airway lumenal area, even at the lowest dose compared with control (#P < 0.01).