Stimulating action of catecholamines on isolated preparations of the rat colon and human and rabbit taeniae coli

Abstract

1 Adrenaline and noradrenaline induced dose related relaxations of the superfused rat colon. The relaxations were progressively transformed into contractions when β-adrenoceptors were blocked with increasing doses of oxprenolol. 2 Since phentolamine or phenoxybenzamine inhibited the contractions induced by adrenaline or noradrenaline in the presence of oxprenolol, it is assumed that the contractions are caused by stimulation of excitatory α-adrenoceptors. 3 Human and rabbit taeniae coli showed responses that were qualitatively similar to those observed with the rat colon.