Relaxation and contraction responses to histamine in the human lung parenchymal strip

The action of histamine on the human lung parenchymal strip preparation was investigated. Histamine produced relaxation at low concentrations and contraction at higher concentrations. Mepyramine, an H1-receptor antagonist partially inhibited both relaxation and contraction responses. The H2-receptor antagonists, cimetidine and metiamide were without significant effect. Propranolol, disodium cromoglycate (DSCG) and atropine did not alter histamine responses. Indomethacin, in some experiments, potentiated the contractile responses to histamine.