text: The Schild plots for the competitive antagonists WB4101 and 5-methyl-urapidil against << alpha 1a-adrenoceptor >>-selective agonist [[ methoxamine ]]-induced contraction were linear and had slopes not significantly different from unity, with a pA2 of 9.07 +/- 0.07 (n = 5) for WB4101 and 9.09 +/- 0.05 (n = 3) for 5-methyl-urapidil.