CHEMBL3889156

FRET-Based Membrane Potential Assay: Two days prior to the experiment, frozen HEK293 cells stably expressing recombinant human Nav1.8 (Essen, Ann Arbor, Mich.) were quickly thawed and plated at 22,500 cells/well in growth medium [MEM (Invitrogen #11095) with 10% FBS (Invitrogen #10082), 1 mM sodium pyruvate (Invitrogen, #C11360), 10 units/mL penicillin 10 U/mL streptomycin 29.2 ug/mL glutamine ((PSG 1%, Invitrogen #10378), 400 ug/mL zeocin (Invitrogen #R250) in black-walled, clear-bottom 384-well poly-D-lysine-coated assay plates (Greiner Bio-One, Frickenhausen, Germany) and incubated in a humidified 5% CO2 incubator at 37° C. On the day of the assay, medium was removed by aspiration, and cells were washed with assay buffer [HBSS (Invitrogen, Carlsbad, Calif.) containing 20 mM HEPES (Invitrogen, Carlsbad, Calif.)]. After washing, 30 uL assay buffer containing the fluorescent voltage-sensor probe CC2-DMPE (Invitrogen, Carlsbad, Calif.) at 20 uM and 0.01% pluronic F-127 (Invitrogen, Carlsbad, Calif.) was added to the cells. Cells were incubated for 40 minutes at room temperature in the dark. Following the incubation, the cells were washed and 30 uL assay buffer containing 2.5 uM DiSBAC2(3) substrate (Invitrogen, Carlsbad, Calif.) and 0.5 mM VABSC-1 (Invitrogen, Carlsbad, Calif.) was added to the cells. The cells were incubated for 60 minutes at room temperature in the dark. Fluorescence readings were made using a FLIPR TETRA(Molecular Devices, Sunnyvale Calif.) equipped with voltage-sensor probe optics. The depolarizing agent, veratridine (Sigma-Aldrich, St. Louis, Mo.), was made up at 3ÿ concentrations in assay buffer containing 1 mg/mL scorpion venom (SVqq, from Leiurus quinquestriatus; Sigma-Aldrich, St. Louis, Mo.).