HISTAMINE RECEPTORS IN THE BRONCHIAL MUSCULATURE AND VASCULATURE OF THE DOG

Abstract

Participation of histamine H₁-and H₂-receptors in the bronchial musculature and vasculature of the dog was investigated by using the method for evaluating airway responses. A peristaltic pump and a Starling pneumatic resistance were used for a constant pressure perfusion. Dogs given 0.1-10μg histamine by a close intraarterial injection showed increases in ventilation overflow (bronchoconstriction) and in blood flow (bronchial vasodilatation) in a dose-dependent manner. The bronchoconstriction produced by histamine was antagonized strongly by chlorpheniramine, a H₁-receptor antagonist, but not modified by cimetidine, a H₂-receptor antagonist. The bronchial vasodilatation produced by histamine was antagonized by both chlorpheniramine and cimetidine. These results suggest that histamine evokes bronchoconstriction through H₁-receptors and bronchial vasodilatation through H₁-and H₂-receptors.