RESPIRATORY SYSTEM MECHANICS IN MICE MEASURED BY END-INFLATION OCCLUSION

Characterization of pulmonary function parameters in mice will facilit ate the dissection of genetic mechanisms underlying airway hyperrespon siveness We evaluated acetylcholine (ACh)-induced respiratory system r esistance (Rrs) and elastance (Ers) in A/J and C3H/HeJ mice and compar ed these results with the previously used airway pressure-time index ( APTI). A low-dead-space ventilatory system was designed to ventilate a nesthetized mice with constant inspiratory flow. The end-inflation occ lusion method was used to measure Rrs and Ers at baseline and after in travenous ACh (12.5-75.0 mu g/kg) challenge. ACh induced a dose-depend ent rise in Rrs and Ers in A/J mice, whereas minimal changes were obse rved in C3H/HeJ mice. A/J mice had a higher baseline Rrs, yet the resp onse to ACh was independent of baseline Rrs. Additionally, sequential ACh challenges led to augmented responses. Rrs, Ers, and APTI were str ongly correlated, and each was useful to detect differences in interst rain cholinergic-induced airway responsiveness. The Rrs detected the s mallest differences between the strains of mice studied.