| Assay Method Information | |
| | Inhibition of Specific Binding to the Rat NR1/NR2B Receptor |
| Description: | The assay depends on the binding of a tracer to the GluN2B subunit-containing NMDA receptors and the ability of the test compounds to displace such binding. 3-[3H] 1-(azetidin-1-yl)-2-[6-(4-fluoro-3-methyl-phenyl)pyrrolo[3,2-b]pyridin-1-yl]ethanone is a high-affinity GluN2B-selective antagonist, which binds to the Ifenprodil binding site located at the interphase between GluN1 and GluN2B subunits. Alternatively, The assay measures binding affinity for ligands that compete for the Ifenprodil binding site in the native NMDA receptors from adult rat cortical membranes.In brief, rat adult cortex is homogenized in the assay buffer (50 mM Tris; pH 7.4). The resulting cortical membranes containing native NMDA receptors are purified by centrifugation and extensively washed, then re-suspended in the assay buffer. The test compounds, tracer and membranes are mixed together and incubated with shaking for 2 hours at room temperature to reach binding equilibrium. Non-specific binding of the tracer is determined by pre-incubation of brain membranes with 10 μM of CP 101,606. Following the incubation, the bound and unbound tracer is separated by filtration with cell harvester and GF/B filter plates (PerkinElmer) soaked with polyethylenimine.The extent of binding is measured by counting [3H] radioactivity retained on the filters plates with liquid scintillator counter. Binding affinity (equilibrium dissociation constant Ki) for the test compounds is determined by fitting experimental data with the following model log EC50=log(10^ log Ki*(1+[Radioligand]/HotKd)) and Y=Bottom+(Top-Bottom)/(1+10^(X-Log EC50)) where [Radioligand] is the concentration of the tracer, HotKdNM is the equilibrium dissociation constant of the tracer, Top and Bottom are the curve plateaus in the units of Y axis.HNR2BC: Effects of Test Articles on Cloned Human NR1/NR2B Ion Channels Expressed in Mammalian CellsNMDA 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 137 mM NaCl, 4 mM KCl, 2 mM CaCl2, 0.5 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 (137 mM NaCl, 4 mM KCl, 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 is used to maximize the assay's signal window and ability to detect NMDA receptor antagonists and negative allosteric modulators. 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 | |
|---|---|
| If you find an error in this entry please send us an E-mail | |