title: Bronchial spasmolytic action of terbutaline and fenoterol compared with that of ipratropium bromide in the anaesthetized dog.
abstract: Continuous recordings of heart rate, respiration rate, minute volume and bronchial resistance were made over a period of altogether three hours in spontaneously breathing dogs anaesthetized with chloralose. At hourly intervals, before and 1 and 2 hr after the administration of bronchodilators, bronchial spasm was induced by inhalation of an acetylcholine solution. Two beta2-stimulants, terbutaline and fenoterol, were administered by inhalation in doses of 0.5, 0.16 and 0.05 mg/kg and 0.1, 0.3 and 0.01 mg/kg respectively. For comparison, an atropine derivative, ipratropium bromide, was also given by the same route in doses of 0.04 and 0.01 mg/kg. Controls received normal saline. Terbutaline and fenoterol 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 hr after the administration of terbutaline, and by 15--70% after fenoterol. 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 hr after doses of 0.04 and 0.01 mg/kg, respectively. Fenoterol had a slightly greater central stimulant effect than terbutaline; ipratropium bromide displayed no stimulant activity.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000403:Airway Resistance / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology*; D001986:Bronchial Spasm / Q000139:chemically induced*; D004285:Dogs; D004983:Ethanolamines / Q000494:pharmacology*; D005280:Fenoterol / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects; D009241:Ipratropium / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D013726:Terbutaline / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D001286:Atropine Derivatives; D004983:Ethanolamines; D005280:Fenoterol; D009241:Ipratropium; D013726:Terbutaline; D000109:Acetylcholine