text: In beta-escin-skinned strips of chloroethylclonidine-pretreated smooth muscle, the enhancement of Ca2+ contraction produced by norepinephrine was significantly decreased, whereas the amplitude was the same as that produced by methoxamine or clonidine; this enhancement was inhibited by the selective << alpha 1A-adrenoceptor >> antagonist [[ WB 4101 ]] (100 nM).