Reflex Decrease of Histamine-induced Bronchoconstriction after Laryngeal Stimulation in Asthmatic Patients

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Abstract
The aim of this work was to determine if the nonadrenergic noncholinergic nervous system can be reflexly activated in asthmatic patients by stimulating the vocal cords. The stimulation was produced by a cytology brush passed through a bronchoscope previously introduced transnasally and positioned just above the epiglottis. The subjects were premedicated with cholinergic blockers, and bronchoconstriction was induced by inhalation of histamine. In 11 experiments performed on six patients, vocal cords stimulation resulted in a decreased Rl from 8.4 ± 1.0 to 6.3 ± 0.8 cm H2O·L−1· (mean ± SE) (p < 0.01). To assess the possible contribution of circulating catecholamines to this decrease, plasma epinephrine and norepinephrine levels were measured in six experiments, before and 30 s, 1, 3, and 5 min after the stimulation. Pulmonary resistance fell from 10.0 ± 1.3 to 7.6 ± 0.9 cm H2O·L−1·s (mean ± SE) (p < 0.05) 30 s and to 7.9 ± 0.9 cm H2O·L−1·s (p < 0.05) 60 s after stimulation. Epinephrine and norepinephrine levels increased slightly but not significantly throughout the experiment. We conclude that in asthmatic patients, as in normal subjects, stimulation of the vocal cords produces a reflex decrease in histamine-induced bronchoconstriction which is modulated by the nonadrenergic noncholinergic nervous system.