Measurement of calcium flux through ionotropic glutamate receptors using Cytostar-T scintillating microplates

Human embryonic kidney cells (HEK293), expressing the human GluR4 receptor sub-unit of 2-amino-3-hydroxy-methylisoxazol-4-ylpropionic acid (AMPA) type non-NMDA receptors were used, in combination with Cytostar-T scintillating microplates, to develop an assay system for the screening of novel compounds with potential AMPA antagonistic characteristics. Agonist dose responses were measured using the agonists: AMPA; quisqualic acid; L-glutamic acid and kainic acid (KA), and EC50 values of 40, 10, 100 and 100 microM were estimated for each of the agonists, respectively. The AMPA receptor antagonists LY293558 and GYK152466 were tested and shown to inhibit agonist induced [45Ca] influx into the cells. An IC50 value of 600 microM was estimated for the competitive antagonist LY293558 and a value of 100 microM estimated for the non-competitive antagonist GYK152466. The developed assay system is homogeneous, allowing increased assay precision and speed. This allows the potential for automation of the assay and it may be used for screening large numbers of novel compounds.