title: Relaxant responses by optical isomers of ephedrine and methylephedrine in guinea pig tracheal smooth muscle.
abstract: The effects of optical isomers of ephedrine and methylephedrine on the guinea pig tracheal smooth muscle were studied. l-Ephedrine markedly caused a graded relaxation of the guinea pig trachea where the tone had been raised spontaneously. A rightward shift of the l-ephedrine concentration-response curve was observed for propranolol and butoxamine, and the pA2 values for propranolol and butoxamine were 8.55 and 6.38, respectively. d-Methylephedrine markedly caused a graded relaxation of the guinea pig trachea contracted with histamine. Propranolol and bupranolol did not affect the relaxant response to d-methylephedrine. d-Methylephedrine competitively antagonized the contractile responses to histamine, and the pA2 value for d-methylephedrine was 5.12. These results suggest that l-ephedrine-induced relaxation of the guinea pig trachea is mediated through beta 2-adrenoceptors, whereas d-methylephedrine relaxes the guinea pig trachea by blocking histamine receptors.
authors.affiliation: Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Koike
authors.forename: T
authors.initials: T
authors.lastname: Kawasuji
authors.forename: H
authors.initials: H
authors.lastname: Saito
authors.forename: M
authors.initials: M
authors.lastname: Matsumoto
authors.forename: N
authors.initials: N
authors.lastname: Yasuda
authors.forename: S
authors.initials: S
authors.lastname: Niizawa
authors.forename: I
authors.initials: I
authors.lastname: Takayanagi
mesh_terms: D000818:Animals; D002078:Butoxamine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004809:Ephedrine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D013237:Stereoisomerism; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
chemical_list: D002078:Butoxamine; C041707:N-methylephedrine; D006632:Histamine; D002217:Carbachol; D011433:Propranolol; D004809:Ephedrine