Repetitive measurements of pulmonary mechanics to inhaled cholinergic challenge in spontaneously breathing mice

TLDR

Precise and repeatable measurements of pulmonary function in intact mice are increasingly important for experimental investigations of respiratory disorders such as asthma. The study aims to validate a novel in vivo method that combines direct, repetitive pulmonary mechanics recordings with aerosolized cholinergic challenges in spontaneously breathing mice, to provide essential data for respiratory disorder research. The method involves direct, repetitive recordings of standard pulmonary mechanics combined with aerosolized cholinergic challenges in anesthetized, orotracheally intubated, spontaneously breathing mice. The approach yielded reproducible, dose‑dependent increases in pulmonary resistance and dynamic compliance in nonsensitized BALB/c mice without cytological or histological damage, while allergic mice exhibited significantly greater responsiveness, eosinophilia, lymphocytosis, and laryngotracheal pathology.

Abstract

Precise and repeatable measurements of pulmonary function in intact mice are becoming increasingly important for experimental investigations on various respiratory disorders including asthma. Here, we present validation of a novel in vivo method that, for the first time, combines direct and repetitive recordings of standard pulmonary mechanics with cholinergic aerosol challenges in anesthetized, orotracheally intubated, spontaneously breathing mice. We demonstrate that, in several groups of nonsensitized BALB/c mice, dose-related increases in pulmonary resistance and dynamic compliance to aerosolized methacholine are reproducible over short and extended intervals without causing detectable cytological alterations in the bronchoalveolar lavage or relevant histological changes in the proximal trachea and larynx regardless of the number of orotracheal intubations. Moreover, as further validation, we confirm that allergic mice, sensitized and challenged with Aspergillus fumigatus, were significantly more responsive to cholinergic challenge (P < 0.01) and exhibited marked eosinophilia and lymphocytosis in bronchoalveolar lavage fluids as well as significant pathological alterations in laryngotracheal histology compared with nonsensitized mice. We suggest that this approach will provide useful and necessary information on pulmonary mechanics in studies of various respiratory disorders in mice, including experimental models of asthma and chronic obstructive pulmonary disorder, investigations of pulmonary pharmacology, or more general investigations of the genetic determinants of lung function.