Relaxant and β2-adrenoceptor blocking activities of labetalol, dilevalol, amosulalol and KF-4317 on the rat isolated aorta

Abstract The KCl-contracted rat aorta is relaxed by labetalol, dilevalol, amosulalol and KF-4317. These relaxations are not reversed by ICI 118,551 at 10−6 M and, therefore, are not due to β-adrenoceptor agonism. At 10−7 M, labetalol, dilevalol, amosulalol and KF-4317 were β2-adrenoceptor antagonists as they inhibited the relaxant responses of rat aorta to procaterol.