Abstract
β-Adrenoceptor subtypes mediating relaxation were examined by using pharmacological and molecular analyses in guinea-pig esophageal muscularis mucosae. (−)-Isoprenaline-induced relaxations were antagonized by (±)-propranolol (p A 2=8.47±0.07), a selective β 1-adrenoceptor antagonist, (±)-2-hydroxy-5-[2-[[2-hydroxy-3-[4-[1-methyl-4-(trifluoromethyl)-1 H-imidazol-2-yl]phenoxy]propyl]amino]ethoxy]-benzamide methanesulfonate (CGP20712A; p A 2=9.43±0.09), and a selective β 2-adrenoceptor antagonist, (±)-1-[2,3-(dihydro-7-methyl-1 H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride (ICI-118,5511; p A 2=7.11±0.04), indicating that β 1-adrenoceptors but not β 2- or β 3-adrenoceptors were essentially involved in β-adrenoceptor-mediated relaxations. However, the expression of messenger RNA (mRNA) for β 1- and β 2-adrenoceptors, but not for β 3-adrenoceptors, was detected by reverse transcription-polymerase chain reaction (RT-PCR). These results clearly suggest that not all β-adrenoceptor mRNA expressed strictly reflect functional receptors in guinea-pig esophageal muscularis mucosae.
Published Version
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