Effect of histamine on human bronchial arteries in vitro

Summary Histamine caused a concentration-dependent relaxation at lower concentrations (1 pmol/1–1 mol/l) and contraction at higher concentrations (0.01–1 mmol/l) of isolated precontracted human bronchial arteries. In the vessels at resting tension only concentration-dependent contraction was evoked by histamine (0.01–1 mmol/l). Both the contractile and relaxant responses were significantly antagonised by mepyramine (1 gmol/l), with an estimated pK_B value of 8.4, but not by cimetidine (100 mol/l). Our results indicate that histamine induces biphasic effects on human bronchial arteries via H₁-re-ceptors. Send offprint requests to P. J. Barnes at the above address