| Assay Method Information | |
| | In Vitro Assay |
| Description: | 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 uL of staining buffer (HBSS containing 1% FCS, 20 mM HEPES, NaHCO3: 0.375 g/L, 5 mM probenecid (Sigma) and 3 uM 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 uL/well, incubated for 120 min and finally 10 uL/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. The IC50 value (the concentration of compound needed to inhibit 50% of the agonistic response) is determined and may be normalized using the obtained IC50 value of an on-plate reference compound. Optimized conditions were achieved by adjustment of pipetting speed and cell splitting regime. The calculated IC50 values may fluctuate depending on the daily cellular assay performance. Fluctuations of this kind are known to those skilled in the art. In the case where IC50 values have been determined several times for the same compound, the geometric mean has been given. |
| Affinity data for this assay | |
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