The beta2- and beta3-adrenoceptor-mediated relaxation induced by fenoterol in guinea pig taenia caecum.
Fenoterol, a beta2-adrenoceptor selective agonist, belongs to the arylethanolamine class. To understand the receptor subtypes responsible for beta-adrenoceptor-mediated relaxation of guinea pig taenia caecum, we investigated the effect of fenoterol. Fenoterol caused concentration-dependent relaxation of the guinea pig taenia caecum. Propranolol, bupranolol and butoxamine produced shifts of the concentration-response curve for fenoterol. Schild regression analyses carried out for propranolol, butoxamine and bupranolol against fenoterol gave pA2 values of 8.41, 6.33 and 8.44, respectively. However, in the presence of 3 x 10(-4) M atenolol, 10(-4) M butoxamine and 10(-6) M phentolamine to block the beta1-, beta2- and a-adrenoceptor effects, respectively, Schild regression analysis carried out for bupranolol against fenoterol gave pA2 values of 5.80. These results suggest that the relaxant response to fenoterol in the guinea pig taenia caecum is mediated by both the beta2- and the beta3-adrenoceptors.
Akimoto
Yurie
Y
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, 2-2-1, Miyama, Funabashi, Chiba 274-8510, Japan. yurie@phar.toho-u.ac.jp
Horinouchi
Takahiro
T
Tanaka
Yoshio
Y
Koike
Katsuo
K
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000818:Animals; D002046:Bupranolol / Q000008:administration & dosage; D002078:Butoxamine / Q000008:administration & dosage; D002432:Cecum / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005280:Fenoterol / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D011433:Propranolol / Q000008:administration & dosage; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology*; D022702:Receptors, Adrenergic, beta-3 / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D018343:Receptors, Adrenergic, beta-2; D022702:Receptors, Adrenergic, beta-3; D002078:Butoxamine; D005280:Fenoterol; D002046:Bupranolol; D011433:Propranolol