Exercise-induced bronchospasm: Effect of adrenergic or cholinergic blockade

To assess the role of the autonomic nervous system in the bronchospasm which occurs in asthmatic children following exercise, β-adrenergic, α-adrenergic, or cholinergic blockade was induced by the intravenous injection of propranolol, phentolamine, or atropine, respectively, with saline as a control. Treatments were given by random assignment once to each of 10 asthmatic children on each of four successive afternoons, with each child acting as his own control. Measurement of peak expiratory flow rates (PEFR) before injections, 15 minutes later before standard treadmill exercise, and 10 minutes after completion of 8 minutes of exercise disclosed a significant decrease in PEFR following injection with propranolol only. Pulse rate alterations were consistent with the various kinds of blockade sought. None of the treatments affected the decrease in PEFR induced by exercise. It seems unlikely, therefore, that exercise-induced bronchospasm is mediated in major fashion by the autonomic nervous system.