| Assay Method Information | |
| | NMDA receptor FLIPR assay |
| Description: | NMDA receptors are ion channels that are highly permeable to Ca2+ ions, rendering it possible to monitor NMDA receptor function using cell-based calcium flux assay. In this assay, co-agonists glutamate and glycine are added to cells heterologously expressing human GluN1/GluN2B NMDA receptors to initiate cellular Ca2+ influx. The time course of the changes in intracellular calcium is measured using a fluorescent dye and a FLIPR (Fluorometric Imaging Plate Reader) device.Twenty four hours before measurements, the expression of the NMDA receptors in the stable cell line is induced with Tet-On inducible system in the presence of a non-selective NMDA receptor blocker. On the day of the experiment, cell culture media is carefully washed and the cells are loaded with Calcium 5 Dye Kit (Molecular Devices) in dye loading buffer containing 149 mM NaCl, 4 mM KCl, 2 mM CaCl2, and 1.5 mM MgCl2, 10 mM HEPES and 5 mM D-glucose; pH 7.4. After 1 h incubation at the room temperature, the dye is washed away with the assay buffer (149 mM NaCl (standard assay) or 150 mM (HTS assay), 4 mM KCl (standard assay) or 3 mM (HTS assay), 2 mM CaCl2, 0.01 mM EDTA, 10 mM HEPES and 5 mM D-glucose; pH 7.4) In the FLIPR TETRA reader, various concentrations of the test compounds are added to the cells for 5 min while fluorescence is monitored to detect potential agonist activity. Next, co-agonists, glutamate and glycine are added for another 5 minutes. The concentration of glutamate corresponding to EC80 (standard assay) or EC40 (HTS assay) is used to maximize the assay's signal window or the ability to detect NMDA receptor antagonists and negative allosteric modulators, respectively. A saturating concentration (10 μM) of glycine is also present in the assay. A non-selective NMDA receptor antagonist, (+)MK-801 is used as a positive control for antagonist activity. The fluorescent signal in the presence of test compounds is quantified and normalized to the signal defined by the appropriate control wells. |
| Affinity data for this assay | |
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