Schild-plot for 18-MC-induced inhibition of [3H]TCP binding to the Torpedo AChR in the desensitized/CCh-bound state. (A) AChR-rich membranes (0.3 μM nAChR) were equilibrated with [3H]TCP, in the presence of 1 mM CCh (desensitized state), at initial PCP concentrations of 0 (control; ■), 3.1 (Δ),6.3 (□),and 9.4μM (○), respectively. The apparent IC50 values were calculated by nonlinear least-squares fit according to Eq. (2). Shown is the average of experiments performed in triplicate. (B) Modified Schild-plot for 18-MC-induced inhibition of [3H]TCP binding. The plot shows a linear relationship with a r2 value of 0.92. Shown is the result of experiments performed in triplicate, where the error bars represent the standard deviation (S.D.) values.