Figure 1.

Amount of the B₂ receptor radioligand [¹²⁵I]HPP-Hoe 140 (left panels) and B₁ receptor radioligand [¹²⁵I]HPP-[des-Arg¹⁰]-Hoe140 (right panels) bound to the spinal trigeminal nucleus (SP5) of 8-week-old SHR (n=4) and age-matched WKY (n=4) as a function of their concentrations. Specific binding is calculated as the mathematical difference between total and nonspecific (NS) binding, which persists in the presence of 1 μM of unlabelled ligand (upper panels). The affinity of the binding, which is expressed as a dissociation constant (K_d), was calculated as the concentration of B₂ or B1 radioligand that results in 50% of maximal specific binding (lower panels).