title: Effects of histamine H2-receptor agonists and antagonists on isolated guinea-pig airway muscles.
abstract: The effects of histamine H2-receptor agonists and antagonists on isolated guinea-pig lung parenchymal and tracheal strips were investigated. Dimaprit, 10(-7) to 10(-3) M, produced dose-dependent relaxation of parenchymal strips while at 10(-3) M, tracheal strips relaxed only partially. Pretreatment of parenchymal strips with cimetidine or YM-11170, H2-receptor antagonists, resulted in a parallel shift of the dimaprit dose-response curve to the right. 4-Methylhistamine produced relaxation of parenchymal strips in a bell-shaped dose-related manner; at high concentrations, it effected the contraction of tracheal strips. In mepyramine-pretreated parenchymal and tracheal strips, 4-methylhistamine induced dose-dependent relaxation, indicating that at high concentrations, it stimulates two functionally opposite receptors, H1 and H2. These results suggest that there are H2-receptors in guinea-pig airways, predominantly in the periphery.
mesh_terms: D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D017259:Dimaprit; D004347:Drug Interactions; D006168:Guinea Pigs; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011968:Receptors, Histamine / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D013890:Thiourea / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects
chemical_list: D006635:Histamine H2 Antagonists; D008761:Methylhistamines; D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; C025566:4-methylhistamine; D002927:Cimetidine; D013890:Thiourea; D017259:Dimaprit