CHEMBL5730355

Fluorescent Imaging Plate Reader (FLIPR) Assay: Orexin antagonist activity was determined by measuring changes in intracellular calcium levels using a Ca2+ sensitive fluorescent dye. The changes in fluorescent signal were monitored by Fluorescent Imaging Plate Reader (FLIPR) technology available from Molecular Devices, LLC, U.S.A. Orexin mediated increases in intracellular Ca2+ concentration were readily detected upon activation with orexin-A. Twenty-four hours prior to the assay, RBL-2H3 cells stably expressing either human orexin receptor 1 or human orexin receptor 2 were seeded in cell culture medium in black, clear-bottom 384-well plates (commercially available from Corning Inc., U.S.A.) and grown overnight at 37° C., 5% CO2. On the day of the assay, cell culture media was removed and cells were loaded with Calcium 5 Dye (commercially sold by Molecular Devices, LLC, U.S.A.) for 1 hour at 37° C., 5% CO2. Test compounds (at 10 point half log concentration response curves from 10 uM) were added to cells for 15 minutes prior to the addition of orexin-A to all wells, to achieve a final concentration that produces approximately an 80% maximal response. The IC50 values were determined from ten point concentration response curves. Curves were generated using the average of two wells for each data point.