Figure 7.

Effect of allosteric M₂R modulator 14 on the saturation binding of [³H]64 determined at CHO-hM₂R cell homogenates at 22 °C. (A) Isotherms of specific radioligand binding plotted in the linear and semilogarithmic scale. The presence of compound 14 led to a rightward shift of the saturation isotherms of [³H]64. (B) “Schild” regression resulting from the rightward shifts (ΔpK_d) of the saturation isotherms [log(r – 1) plotted vs log(concentration 14), where r = 10^ΔpK_d]. The slope of the linear Schild regression was not different from unity [P > 0.5, based on the slope mean value ± SEM (0.99 ± 0.15) from three sets of independent saturation-binding experiments (performed in triplicate)], suggesting a competitive interaction between [³H]64 and 14. Data represent mean values ± SEM from three independent experiments (each performed in triplicate).