2.6. Airway hyperresponsiveness (AHR)
Airway hypersensitivity was measured by methacholine-induced airway contraction using a plethysmograph (OCP-3000, Allmedicus, Anyang, Korea) after 24 h of final OVA inhalation. Each mouse was put into the body record box of whole-body plethysmograph nebulized with 10-80 mg/mL methacholine for 3 min at each increasing concentration. The airway term was measured for 3 min after inhalation with a haze for 3 min while increasing the methacholine concentration. Enhanced pause (Penh) is an indicator of the airway term obtained by the following formular:
Penh = (Te/Tr-1) × PEF/PIF
Where Te is expiratory time (sec), Tr is relaxation time (sec), PEF is peak expiratory flow (mL/sec), and PIF is peak inspiratory flow (mL/sec).