Assay Method Information

Assay Name:  Human D1 Receptor Binding Assay
Description:  D1 binding assays were performed using over-expressing LTK human cell lines. To determine basic assay parameters, ligand concentrations were determined from saturation binding studies where the Kd for [3H]-SCH23390 was found to be 1.3 nM. From tissue concentration curve studies, the optimal amount of tissue was determined to be 1.75 mg/mL per 96 well plate using 0.5 nM of [3H]-SCH23390. These ligand and tissue concentrations were used in time course studies to determine linearity and equilibrium conditions for binding. Binding was at equilibrium with the specified amount of tissue in 30 minutes at 37° C. From these parameters, Ki values were determined by homogenizing the specified amount of tissue for each species in 50 mM Tris (pH 7.4 at 4° C.) containing 2.0 mM MgCl2 using a Polytron and spun in a centrifuge at 40,000×g for 10 minutes. The pellet was resuspended in assay buffer [50 mM Tris (pH 7.4@ RT) containing 4 mM MgSO4 and 0.5 mM EDTA]. Incubations were initiated by the addition of 200 μL of tissue to 96-well plates containing test drugs (2.5 μL) and 0.5 nM [3H]-SCH23390 (50 μL) in a final volume of 250 μL. Non-specific binding was determined by radioligand binding in the presence of a saturating concentration of (+)-Butaclamol (10 μM), a D1 antagonist. After a 30 minute incubation period at 37° C., assay samples were rapidly filtered through Unifilter-96 GF/B PEI-coated filter plates and rinsed with 50 mM Tris buffer (pH 7.4 at 4° C.). Membrane bound [3H]-SCH23390 levels were determined by liquid scintillation counting of the filterplates in Ecolume. The IC50 value (concentration at which 50% inhibition of specific binding occurs) was calculated by linear regression of the concentration-response data in Microsoft Excel. Ki values were calculated according to the Cheng-Prusoff equation.
Affinity data for this assay
 

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