title: Comparison of the effects of histamine H1- and H2-receptor agonists on large and small airways in normal and asthmatic subjects.
abstract: It is accepted that histamine H1-receptors are present on human bronchial smooth muscle and that they mediate bronchoconstriction. However, the role of the histamine H2-receptor in the airways of man is less certain. In ten non-asthmatic and five asthmatic subjects we have compared the effects of inhalation of a specific H1-receptor agonist, betahistine, a specific H2-receptor agonist, impromidine and the combined H1- and H2-receptor agonist, histamine, on specific airways conductance and measurements from partial expiratory flow-volume curves. Both histamine and betahistine induced reproducible dose-dependent bronchoconstriction in all subjects, as assessed by all measurements made. Impromidine had no effect on measurements of airways function in either group of subjects. These results confirm the presence of bronchoconstricting H1-receptors, and the absence of significant numbers of H2-receptors on human bronchial smooth muscle. There is no difference in the distribution of these receptors in normal and asthmatic subjects.
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000187:drug effects*; D001249:Asthma / Q000503:physiopathology*; D001621:Betahistine / Q000494:pharmacology*; D001980:Bronchi / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D017446:Impromidine; D011725:Pyridines / Q000494:pharmacology*; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*
chemical_list: D007093:Imidazoles; D011725:Pyridines; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D017446:Impromidine; D001621:Betahistine