Dopaminergic Modulation of Human Bronchial Tone

Abstract

Background: Dopamine exerts inhibitory and excitatory effects on different systems, independently from its adrenergic action. Its effects on bronchial tone in man have not been well studied. We examined its possible modulating effect on bronchial diameter, administering inhaled and intravenous dopamine and DA2 blockers (metociopramide) to subjects with various degrees of bronchial tone. Methods: We examined 60 volunteers. In all of them we measured arterial blood pressure and heart rate and by spirometry we measured FVC, FEV1, FEFmax and FEF50 before and after each procedure. We administered dopamine: a) through inhalation (0.5 μg/kg/min) to 10 healthy subjects, nine with asthma without acute bronchospasm (AWAB) and 18 with acute asthma attack (AAA); b) 0.5 μ/kg/min intravenous to one healthy subject and to another with AWAB. We administered intravenous metoclopramide (7 μg/kg/min) to 10 healthy subjects and 10 with AWAB. Statisfics: Studenf’s "t" test, Wilcoxon’s and Mann Whitney tests. Results: Inhaled dopamine increased FEV1 and FVC, FEFmax and FEF50 in the AAA group, but there were no modifications in the healthy group nor in the AWAB group neither by inhalation or by the intravenous route. Metoclopramide did not produce any changes of respiratory parameters in healthy individuals, nor in those with AWAB. Conclusions: 1) Inhaled dopamine produces bronchial tone inhibition when the basal tone is increased during acute asthma attack. 2) lt does not modify the basal tone in healthy individuals, nor in those with AWAB. 3) DA2 blockade does not modify basal bronchial tone neither in healthy subjects nor in those with AWAB.