Early bronchoconstriction after allergen challenge of nonanesthetized guinea pigs

Background: Bronchial asthma is a complex disease, which is characterized by spontaneous exacerbations of airway obstruction and persistent bronchial hyperresponsiveness. Animal models have fallen short of reproducing the human disease, particularly in mimicking the spontaneous and persistent airflow obstruction that characterized in asthma. In animals, airflow obstruction is usually assessed by measuring airflow resistance during tidal breathing under such invasive technique as tracheostomy and anesthesia. A noninvasive technique for measuring pulmonary function in small animals is needed to evaluate long-term changes in lung function during the course of experimentally produced disease without sacrificing the animal. Purpose: The purpose of this study was to evaluate early bronchoconstriction after allergen challenge and airway responsiveness (AR) to inhaled methacholine in nonanesthetized, unrestrained guinea pigs. Method: Guinea pig model of asthma was sensitized by subcutaneous injection with ovalbumin and challenged by inhalation of aerosolized ovalbumin (1% wt/vol ovalbumin). Airflow obstruction of conscious guinea pig was measured as specific airway resistance (airway resistance x thoracic gas volume). Airway resistance and thoracic gas volume of conscious guinea pig were assessed by body plethysmography before challenge and at regular intervals for as long as 30 minutes after challenge. AR to aerosolized methacholine of asthma grou, was compared with that of control group in body plethysmography. Result: Asthma models developed in 13 (65%) among 20 guinea pigs, in which early responses occurred in airways after the exposure to inhalation with ovalbumin Airway challenge with ovalbumin caused increase in specific airway resistance, which peaked at 6 minutes and amounted to a 231.5 ± 30.4% increase from baseline, AR to aerosolized methacholine of asthma model increased significantly compared with control group. Conclusion: The results have showed a useful animal model to evaluate early bronchoconstriction after allergen challenge and airway responsiveness in nonanesthetized, unrestrained guinea pigs.