Reactivity of trachea, bronchi, and lung strips to histamine and carbachol in rhesus monkeys

Abstract

Responses of isolated airway smooth muscles of a subhuman primate to carbachol and histamine were investigated. Isolated lung parenchymal strips of rhesus monkeys (RM) exhibited approximately equal sensitivity (i.e., ED50) and contractility (i.e., maximum tension) to carbachol and histamine. Tracheal chains and bronchial strips responded with concentration-dependent contractions to carbachol. Trachea did not exhibit any contractile responses to histamine. Bronchial strips responded with weak contractile responses to histamine when compared with those elicited ay carbachol. Histamine-induced contractions on bronchi and lung strips were easily antagonized by pyrilamine (H1-receptor antagonist) (10(-6) to 5 X 10(-6) M). Carbachol-contracted trachea and bronchi responded with relaxations to histamine and dimaprit (H2-receptor agonist) that were antagonized by metiamide (H2-receptor antagonist) (5 X 10(-5) M). The present findings indicate 1) a differential reactivity of central and peripheral airway smooth muscles of RM to histamine and carbachol; 2) lung strips of RM appear to possess only H1 types of histamine receptors; 3) bronchial smooth muscles of RM have a small population of H1-receptors mediating bronchoconstriction; and 4) a preponderance of inhibitory H2-receptors in the tracheobronchial smooth muscles of rhesus monkeys. If these subhuman primate findings apply to the airways of man, they could aid considerably in furthering our understanding of the pathophysiology of the respiratory tract.