| Assay Method Information | |
| | Muscarinic 3 Receptor Binding Assay |
| Description: | The muscarinic 3 receptor binding assay was adapted from Perkin Elmer. Briefly, assay buffer (60 μL of pH 7.4 phosphate saline buffer) was added to polypropylene round bottom 96-well microtiter plates, followed by CHO cell suspension expressing the human M3 receptor (1 mg suspension/ml; 20 ug membrane suspension per well). 3H-Scopolamine (20 μL of a 7.5 nM solution) was added to each well and plates were shaken at room temperature for 2 h. Atropine (Sigma-Aldrich, St. Louis, Mo.) was used as a positive control. Test compounds and control samples were prepared in DMSO (20 mM) and diluted to give a final concentration of 20 μM. The reaction mixtures were then added to matrix 96-well GFC filtration microtiter plates that had been previously pretreated with 0.5% polyethylimine (100 μL) for 4 h and filtered. The binding reactions were terminated by filtering through the GFC plates and washing & filtering with ice-cold phosphate saline buffer (5×100 μL). Once the filters were dry, microscint scintillation cocktail (100 μL) was added to each well, allowed to sit for 20 min and the plates analyzed using a TopCount scintillation counter. Test compounds which showed >50% reduction in 3H-scopolamine binding at a final concentration of 20 μM were subjected to further serial dilutions and evaluated at various concentrations to determine their IC50 value. Curve fitting of % inhibition versus concentration using Excell software allowed determination of IC50 values for test compounds. |
| Affinity data for this assay | |
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