Effects of acute and chronic exposure to nicotine aerosol on bronchial reactivity to inhaled methacholine.

Normal baboons, like humans, demonstrate a wide range of bronchial reactivity to inhaled methacholine. Cigarette-smoking baboons demonstrate reduced bronchial reactivity to inhaled methacholine compared with sham-smoking controls after 6 pack-yr of smoking. To evaluate the role of nicotine in this blunting of airway reactivity, we studied the effects of both acute and chronic nicotine inhalation on reactivity to methacholine in baboons. Inhalation of 2 mg of nicotine had no acute effect on lung function but blunted bronchial reactivity in highly reactive animals. This effect was not diminished after daily inhalation of nicotine for 90 days. Marked interindividual differences in bronchial reactivity to methacholine were not abolished by propranolol, suggesting that factors other than beta-adrenergic tone account for this intersubject variability.