CHEMBL3888045

Scintillation Proximity Assay (SPA): Briefly, serial dilutions of the test compounds were placed in a 96-well plate to which were added SPA beads, membrane and radioligand. The assay conditions for each opioid receptor subtype are described in Table 10 below. The plates were incubated for 8 hours-overnight at room temperature, spun at 1000 rpm to pellet the SPA beads, and radioactivity was measured using the TopCount microplate Scintillation counter. Specific binding at each concentration of test compound was calculated by subtracting the non-specific binding measured in the presence of excess cold ligand. IC50 values were obtained by non-linear regression of specific binding versus concentration curves and Ki values were calculated using Kd values that were experimentally pre-determined for each lot of membrane preparations.