text: Computer-assisted analysis of these curvilinear Schild plots in a two-receptor system indicated that << alpha 1-adrenoceptor >> populations responsible for the constrictive response are predominantly (approximately 80-90%) low affinity sites for the two antagonists (pKd approximately 8.1 for WB4101 and pKd approximately 7.1 for [[ 5-methyl-urapidil ]]) and a small population (approximately 10-20%) are high affinity sites (pKd approximately 9.1 for both WB4101 and 5-methyl-urapidil), which was in good agreement with radioligand binding studies.(ABSTRACT TRUNCATED AT 400 WORDS)