HEK-α1A-Adr, HEK-α1B-Adr, and HEK-α1D-Adr: IP-1 agonist and antagonist dose-response curves. Agonist stimulation of IP-1 formation of α1A-Adr (A), α1B-Adr 1B (B), and (C) α1D-Adr receptor subtypes. Antagonist inhibition of norepinephrine-stimulated IP-1 formation of α1A-Adr (D), α1B-Adr (E), and α1D-Adr (F) receptor subtypes. Data shown are the means ± S.E.M. of three to six experiments, except if a drug had no effect when n = 2.