Involvement of β3-Adrenoceptor in the Relaxation Response in Guinea Pig Taenia Caecum

The Japanese Journal of Pharmacology

Issei Takayanagi¹  Midori Muramatsu¹  Shin-ichi Ohki¹  Takahiro Horinouchi¹  Katsuo Koike¹ 

[1] Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences

关键词: Taenia caecum (guinea pig);    β-Adrenoceptor;    β2-Adrenoceptor;    β3-Adrenoceptor;    CGP 12177;   

DOI  :  10.1254/jjp.66.213

学科分类：药理学

来源: Nihon Yakuri Gakkai Henshuubu / Japanese Pharmacological Society

【 摘 要 】

References(46)Cited-By(21)β-Adrenoceptors in the guinea pig taenia caecum were investigated by measuring relaxation responses to agonists and by a radioligand binding assay using [3H]CGP 12177. The rightward shift of the isoprenaline concentration-response curve was observed by butoxamine, a β2-selective antagonist, and the pA2 value for butoxamine was 6.46. In control preparations, catecholamines caused relaxation with the following rank order of potency: isoprenaline > adrenaline > noradrenaline. However, in the presence of 10-6 M phentolamine, 3 × 10-4 M atenolol and 10-4 M butoxamine, the rank order of potency of the agonists was: isoprenaline > noradrenaline > adrenaline. CGP 12177 caused graded relaxation of the guinea pig taenia caecum, and this response was not influenced by 10-6 M phentolamine, 3 × 10-4 M atenolol, 10-4 M butoxamine or 10-6 M propranolol. The Scatchard plot of the specific [3H]CGP 12177 binding to microsomal fractions from the guinea pig taenia caecum showed two affinity sites of the receptor: high affinity (KD=0.64 nM) and low affinity (KD=142.21 nM) sites. The pKD value of the high affinity site of [3H]-CGP 12177 was in agreement with its pA2 value, and that of the low affinity site was in agreement with its pD2 value. These results suggest that isoprenaline-, noradrenaline- and adrenaline-induced relaxations of the guinea pig taenia caecum predominantly involve β2- and β3-adrenoceptors, whereas CGP 12177-induced relaxation is mediated solely through β3-adrenoceptors.

【 授权许可】

Unknown