CHEMBL5733899

Radioligand Binding Assay: Stably transfected HEK cells expressing the human D2-long and the D3 dopamine receptor were developed using the pIRESneo2 bicistronic expression vector (Clontech, Palo Alto, Calif.). Levels of expression of human D2 and D3 dopamine receptors in HEK cells were 57, 941±14,686 fmol/mg protein and 4202±1516 fmol/mg protein, respectively. Competition curves were performed using 125I-IABN. Membrane homogenates (50 μL) were suspended in 50 mM Tris-HCl/150 mM NaCl/10 mM EDTA buffer, pH 7.5 and incubated with 50 μL of 125I-IABN at 37° C. for 60 min. Nonspecific binding was defined using 4 μM (+)-butaclamol. The radioligand concentration used was approximately equal to the Kd value, and the concentration of the competitive inhibitor ranged over five orders of magnitude. Binding was terminated by the addition of cold wash buffer (10 mM Tris-HCl/150 mM NaCl, pH 7.4) and filtration over a glass-fiber filter (Schleicher and Schuell No. 32). Filters were washed with 10 mL of cold buffer, and the radioactivity was quantitated. A Packard Cobra gamma counter was used for 125I-labeled radioligands (efficiency=75%). The protein concentration was determined using a BCA reagent (Pierce) with bovine serum albumin as the protein standard.