Figure 2.

Competition binding assay. Membranes prepared from transfected COS-7 cells were incubated in the presence of 1.5 nM [³H]EKC and various concentrations of dynorphin A(1–13), bremazocine, spiradoline, or ICI204,448. The specific transfected receptor cDNAs are indicated in the figure. K_i values are listed in Table 1. The amount of radioligand bound in the absence of competing ligand was assigned a value of 100%.