Chest
Clinical InvestigationsIs There Loss of a Protective Muscarinic Receptor Mechanism in Asthma?
Section snippets
Subjects
Fifteen nonsmoker subjects (ten men and five women) without a recent history of upper respiratory tract infection were included in the study. Six subjects had a history of mild asthma; their ages ranged from 25 to 52 years (mean 37). The remaining nine subjects had no personal or family history of atopy. Their ages ranged from 22 to 38 years (mean 30). The asthmatic subjects were asymptomatic at the time of the study, and had not received inhaled beta agonists for at least 12 hours prior to
Baseline Pulmonary Function
These results are shown in Table 1. Asthmatic subjects had evidence of mild airway obstruction as shown by significantly lower SGaw, FEV1 and forced vital capacity. The SGaw was comparable on different experiment days within each group. The mean±SE post-diluent values of SGaw on experiment days 2–5 were 0.21±0.02, 0.21±0.02, 0.20±0.02, and 0.19±0.01 s·cmH2O−1, respectively, for normal subjects, and 0.11±0.03, 0.13±0.02, 0.11±0.02 and 0.12±0.02 s·mH2O−1, respectively, for asthmatic patients.
In
Discussion
The results of this study demonstrate that prior stimulation of airway muscarinic receptors by inhaled methacholine causes a suppression of bronchoconstrictor response to histamine. Suppression of bronchoconstrictor response to histamine by prior muscarinic receptor stimulation was only observed in normals and not in subjects with bronchial asthma. Our study also demonstrates that suppression of histamine responses was specific and only observed after prior muscarinic receptor stimulation. This
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Manuscript received June 12; revision accepted July 13.
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Division of Clinical Pharmacology; recipient of a scholarship from Universidad de Buenos Aires, Argentina.