Histamine modulates dopamine-induced contraction in canine tracheal smooth muscle.

Since exogenous dopamine is commonly used to treat patients of cardiovascular failure, its action on the histamine-sensitized airways is critical for asthmatic subjects. In this study, in vitro canine airway smooth muscle preparation were employed to investigate whether histamine-treatment affects the responsiveness of airway smooth muscle to dopamine. The results of our study demonstrate that, at dopamine tachyphylaxis of canine tracheal smooth muscle, histamine treatment could recover the contraction to dopamine. In the muscle strips sensitized with histamine, the dopamine-induced contraction was decreased by the antagonist to alpha 2-adrenoceptors and increased by the antagonist to beta 1-adrenoceptors. It is concluded that histamine can modulate the dopamine response of canine tracheal smooth muscle by sensitizing, transiently, multiple receptors in the muscle which are responsible for the contractile response to dopamine.