| Assay Method Information | |
| | Intracellular Calcium Assay |
| Description: | Chinese hamster ovary (CHO) cells expressing the human orexin-1 receptor and the human orexin-2 receptor, respectively, are grown in culture medium (Ham F-12 with L-Glutamine) containing 300 μg/mL G418, 100 U/mL penicillin, 100 μg/mL streptomycin and 10% heat inactivated fetal calf serum (FCS). The cells are seeded at 20,000 cells/well into 384-well black clear bottom sterile plates (Greiner). The seeded plates are incubated overnight at 37° C. in 5% CO2. Human orexin-A as an agonist is prepared as 1 mM stock solution in MeOH:water (1:1), diluted in HBSS containing 0.1% bovine serum albumin (BSA), NaHCO3: 0.375 g/L and 20 mM HEPES for use in the assay at a final concentration of 3 nM. Antagonists are prepared as 10 mM stock solution in DMSO, then diluted in 384-well plates using DMSO followed by a transfer of the dilutions into in HBSS containing 0.1% bovine serum albumin (BSA), NaHCO3: 0.375 g/L and 20 mM HEPES. On the day of the assay, 50 μL of staining buffer (HBSS containing 1% FCS, 20 mM HEPES, NaHCO3: 0.375 g/L, 5 mM probenecid (Sigma) and 3 μM of the fluorescent calcium indicator fluo-4 AM (1 mM stock solution in DMSO, containing 10% pluronic) is added to each well. The 384-well cell-plates are incubated for 50 min at 37° C. in 5% CO2 followed by equilibration at rt for 30 min before measurement. Within the Fluorescent Imaging Plate Reader (FLIPR Tetra, Molecular Devices), antagonists are added to the plate in a volume of 10 μL/well, incubated for 120 min and finally 10 μL/well of agonist is added. Fluorescence is measured for each well at 1 second intervals, and the height of each fluorescence peak is compared to the height of the fluorescence peak induced by 3 nM orexin-A with vehicle in place of antagonist. |
| Affinity data for this assay | |
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