| Assay Method Information | |
| | Receptor Binding Assay |
| Description: | The Ki (binding affinity) for μ-receptor was determined with a previously described method using a competitive displacement assay (Neumeyer et al., J. Med. Chem., v. 46, p. 5162-5170, 2003). Membrane protein from CHO (Chinese Hamster Ovarian) cells that stably expressed one type of the cloned human opioid receptor were incubated with 12 different concentrations of the compound in the presence of 0.25 nM [3H]DAMGO, 0.2 nM [3H]naltrindole or 1 nM [3H]U69,593 in a final volume of 1 mL of 50 mM Tris-HCl, pH 7.5 at 25° C. Incubation times of 60 min were used for [3H]DAMGO and [3H]U69,593. Because of a slower association of [3H]naltrindole with the receptor, a 3 h incubation was used with this radioligand. Samples incubated with [3H]naltrindole also contained 10 mM MgCl2 and 0.5 mM phenylmethylsulfonyl fluoride. Nonspecific binding was measured by inclusion of 10 μM naloxone. The binding was terminated by filtering the samples through Schleicher & Schuell No. 32 glass fiber filters using a Brandel 48-well cell harvester. The filters were subsequently washed three times with 3 mL of cold 50 mM Tris-HCl, pH 7.5, and were counted in 2 mL Ecoscint A scintillation fluid. For [3H]naltrindole and [3H]U69,593 binding, the filters were soaked in 0.1% polyethylenimine for at least 60 min before use. IC50 values will be calculated by least squares fit to a logarithm-probit analysis. Ki values of unlabelled compounds were calculated from the equation Ki=(IC50)/1+S where S=(concentration of radioligand)/(Kd of radioligand). |
| Affinity data for this assay | |
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