Dopamine ameliorates bronchoconstriction induced by histaminergic and cholinergic pathways in rabbits.

To clarify the potential of dopamine to alter airway tone in the presence of different bronchoconstrictor stimuli, changes in airway function following dopamine administrations were characterized when the bronchial tone was elevated by stimulating the histaminic or cholinergic pathway. Airway resistance, tissue damping and tissue elastance were measured in anesthetized mechanically ventilated rabbits under baseline conditions, during steady-state bronchoconstriction induced by methacholine or histamine, and following intravenous dopamine (5 and 15 μg/kg/min). Bronchoconstriction induced by methacholine and histamine was significantly ameliorated by dopamine (14.8 ± 2.9% and 14.9 ± 2.9%; p < 0.05 for both), with no difference between the mode of stimuli. Dopamine had no effect on the tissue mechanics. These findings indicate that dopamine relaxes the elevated airway smooth muscle tone without affecting the lung periphery, and this effect is independent of the mode of constrictor stimuli. This profile of dopamine suggests its ability to treat effectively cholinergic and histaminergic bronchoconstriction, besides its positive inotropic effects on the myocardial contractility.