Figure 4. Inhibition of the binding of a series of concentrations of ³H-prazosin and ¹²⁵I-HEAT to α_1A-AR by ρ-Da1a.

Panel A ³H-prazosin binding (from 0.2 to 16 nM) inhibited by ρ-Da1a. Panel B ¹²⁵I-HEAT binding (from 0.1 to 1.25 nM) inhibited by ρ-Da1a. Panel C and D: Fitting, by the Cheng and Prusoff equation IC₅₀ = Ki+Ki(L/Kd), of IC₅₀ values as a function of the radiotracer concentrations.