| Assay Method Information | |
| | Measurement of Antagonistic Activity Against Orexin Receptors |
| Description: | The Chinese hamster ovary (CHO) cell lines CHOOX1R and CHOOX2R were established by modifying CHO cells to constantly express the NFAT-luciferase gene and either the human OX1R or human OX2R gene. Those cells were plated at 10,000 cells/well in 96-well multiplates with DMEM (manufactured by Sigma-Aldrich Co. LLC) supplemented with 5% FBS (manufactured by Thermo Scientific Inc.) and incubated at 37° C. and 5% CO2 for 48 hours. After removal of the medium, 100 μL of an assay buffer (20 mM HEPES (manufactured by Sigma-Aldrich Co. LLC), Hank's balanced salt solution (manufactured by Gibco), 0.1% BSA (manufactured by Sigma-Aldrich Co. LLC), 2.5 mM probenecid acid (manufactured by Wako Pure Chemical Industries, Ltd.), pH 7.4) containing 5 μM Fura-2AM (manufactured by Cayman Chemical Co.) was added to each well, and incubated at 37° C. and 5% CO2 for 60 minutes. After removal of the buffer containing Fura-2AM, 75 μL of the assay buffer was added to each well. Then, 25 L of the assay buffer containing a test compound at various concentrations and OX-A (manufactured by Peptide Institute, Inc.) was added to start the reaction. The change in intracellular calcium ion concentration induced by the reaction was evaluated by the ratio of fluorescent intensities, which were measured at a wavelength of 510 nm based on the two wavelength excitation approach using FDSS 7000 (manufactured by Hamamatsu Photonics K.K.) with fluorescence excitation at 340 nm and 380 nm. A concentration-response curve on the antagonistic activity was plotted from the values of maximal fluorescent intensity ratio determined when various concentrations of a test compound were added in the presence of 300 μM of OX-A, where a value of maximal fluorescent intensity ratio determined by adding 300 pM of OX-A alone corresponds to 100% and a value of maximal fluorescent intensity ratio determined by adding the assay buffer alone corresponds to 0%. Based on the resulting non-linear regression curve, the 50% maximal inhibitory concentration (IC50) was calculated. Each test compound was dissolved in DMSO to a concentration of 10 mM (the final concentration of DMSO was 1%), and then diluted with the assay buffer to give a final concentration of 3.0×10−10 M to 1.0×10−5 M (a common ratio of 3), while OX-A was diluted to a final concentration of 300 pM. The experiment was performed in quadruplicate plates, and the results of the four independent measurements were averaged to give the value of each reaction, and then the IC50 of a sample was calculated. If the sample number was 2 or more, the averaged IC50 was used. |
| Affinity data for this assay | |
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