| Assay Method Information | |
| | Radioligand Binding Assay |
| Description: | HEK-293 cells stably expressing rat TAAR1 were maintained at 37° C. and 5% CO2 in DMEM high glucose medium, containing fetal calf serum (10%, heat inactivated for 30 min at 56° C.), penicillin/streptomycin (1%), and 375 ug/ml geneticin (Gibco). Cells were released from culture flasks using trypsin/EDTA, harvested, washed twice with ice-cold PBS (without Ca2+ and Mg2+), pelleted at 1,000 rpm for 5 min at 4° C., frozen and stored at -80° C. Frozen pellets were suspended in 20 ml HEPES-NaOH (20 mM, pH 7.4) containing 10 mM EDTA and homogenized with a Polytron (PT 6000, Kinematica) at 14,000 rpm for 20 s. The homogenate was centrifuged at 48,000 g for 30 min at 4° C. Subsequently, the supernatant was removed and discarded, and the pellet resuspended in 20 ml HEPES-NaOH (20 mM, pH 7.4) containing 0.1 mM EDTA using the Polytron (20 s at 14,000 rpm). This procedure was repeated and the final pellet resuspended in HEPES-NaOH containing 0.1 mM EDTA and homogenized using the Polytron. Typically, aliquots of 2 ml membrane portions were stored at -80° C. With each new membrane batch the dissociation constant (Kd) was determined via a saturation curve. The TAAR1 radioligand 3[H] (S)-4-[(ethyl-phenyl-amino)-methyl]-4,5-dihydro-oxazol-2-ylamine (described in WO 2008/098857) was used at a concentration equal to the calculated Kd value, that was usually around 2.3 nM, resulting in the binding of approximately 0.2% of the radioligand and a specific binding representing approximately 85% of the total binding. Nonspecific binding was defined as the amount of 3[H] (S)-4-[(ethyl-phenyl-amino)-methyl]-4,5-dihydro-oxazol-2-ylamine bound in the presence of 10 uM unlabeled ligand. All compounds were tested at a broad range of concentrations (10 pM to 10 uM) in duplicates. The test compounds (20 ul/well) were transferred into a 96 deep well plate (TreffLab), and 180 ul of HEPES-NaOH (20 mM, pH 7.4) containing MgCl2 (10 mM) and CaCl2 (2 mM) (binding buffer), 300 ul of the radioligand 3[H] (S)-4-[(ethyl-phenyl-amino)-methyl]-4,5-dihydro-oxazol-2-ylamine at a concentration of 3.3xKd in nM and 500 ul of the membranes (resuspended at 50 ug protein per ml) added. The 96 deep well plates were incubated for 1 hr at 4° C. Incubations were terminated by rapid filtration through Unifilter-96 plates (Packard Instrument Company) and glass filters GF/C (Perkin Elmer) presoaked for 1 hr in polyethylenimine (0.3%) and washed 3 times with 1 ml of cold binding buffer. After addition of 45 ul of Microscint 40 (PerkinElmer) the Unifilter-96 plate was sealed and after 1 hr the ratioactivity counted using a TopCount Microplate Scintillation Counter (Packard Instrument Company). |
| Affinity data for this assay | |
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