[Broncholytic therapy--beta 2 stimulation and vagolysis from an animal experimental viewpoint]

Continuous recordings of heart rate, respiration rate, minute volume and bronchial resistance were made over a period of altogether 3 h in spontaneously breathing dogs anesthetized with chloralose. At hourly intervals, before and 1 and 2 h after the administration of bronchodilators, bronchial spasm was induced by inhalation of an acetylcholine solution. Terbutaline, a beta-stimulant, was administered by inhalation in doses of 0.5, 0.16 and 0.05 mg/kg. For comparison, an atropine derivative, ipratrapium bromide, was given in doses of 0.04 and 0.01 mg/kg. Controls received normal saline. Terbutaline caused an increase in heart rate, respiration rate and minute volume. Acetylcholine-induced bronchial spasm was inhibited to the extent of 10-70% for 2 h after the administration of terbutaline. The acetylcholine antagonist ipratropium bromide caused only transient changes in heart rate, respiration rate and minute volume. Acetylcholine-induced bronchial spasm was inhibited by 95% and 80% for 2 h after doses of 0.04 and 0.01 mg/kg respectively. Terbutaline had a slight stimulant effect; ipratropium bromide displayed no stimulant activity.