Attenuated methacholine airway response following repeat testing in a murine model of allergic airways disease

A progressive attenuation of airway reactivity to methacholine is observed in normal individuals with successive bronchial provocation testing. The absence of this attenuation in asthma is thought to be due airway inflammation. The authors investigated this phenomenon in a mouse model of allergic airways disease. Repeated measurements of airway response were carried out in mice sensitized/challenged with ovalbumin or saline, and in untreated mice. Saline-treated and untreated mice showed reduced airway reactivity following repeated testing. This was also observed in ovalbumin-treated mice in the second and third tests compared to the previous test (P < .05). This attenuation was not associated with airway inflammation, which remained high in the ovalbumin group. The results suggest that attenuation of airway reactivity with repeated methacholine challenge is due to factors other than airway inflammation.