Assay Method Information

Assay Name:  D3 Radioligand Binding Assay
Description:  Compounds were tested for their ability to compete with the orthosteric radioligand [3H]methylspiperone for binding to the D3 DAR using stable HEK cell lines expressing the D3 DAR (Codex Biosciences, Gaithersburg, Md., Catalogue no. CB-80300-206) as described in the detailed protocol below presented in Table 5. Cells were cultured in Dulbecco's modified Eagle's Medium (Corning, catalogue no. 10-013) containing 10% FBS, 1,000 units/mL Penicillin, 1,000 mg/mL Streptomycin, 100 mM sodium pyruvate, 1 μg/mL Gentamicin, and 250 mg/mL G418. All cells were maintained at 37° C. in 500 CO2 and 90% humidity. For radioligand binding assays cells were removed mechanically using calcium-free Earle's balanced salt solution (EBSS). Intact cells were collected by centrifugation and then lysed with 5 mM Tris-HCl and 5 mM MgCl2 at pH 7.4. Homogenates were centrifuged at 30,000×g for 30 minutes. The membranes were re-suspended in EBSS (US Biological, catalogue no. E0249-05) pH 7.4 to a concentration of 16 μg/mL. For competition binding studies, membrane preparations were incubated for 90 minutes at room temperature with various concentrations of compound and a single concentration of [3H]methylspiperone (Perkin Elmer, NET856) in a reaction volume of 250 μL. Non-specific binding was determined in the presence of 4 μM (+)-butaclamol (Sigma-Aldrich, catalogue no. D033). Bound ligand was separated from unbound by filtration through GF/C filters using a PerkinElmer cell harvester and quantified on a Top-count (PerkinElmer). Ki values were determined using Cheng-Prusoff equation from observed IC50 values and ligand Kd values from separate saturation experiments.
Affinity data for this assay
 

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