text: (+)-Tamsulosin, (-)-tamsulosin, SL 89,0591, Rec 15/2739, SNAP 1069 and << RS 17053 >> appeared to act as competitive antagonists of noradrenaline-mediated contractions of rat aorta yielding pA2 affinity estimates which were similar to binding affinities at cloned [[ human alpha 1D adrenoceptors ]].