TABLE 3

Apparent affinities of subunits for CX546 in [³H]AMPA binding tests Binding of [³H]AMPA to subunits GluR2 and GluR3 stably or transiently expressed in human embryonic kidney 293 cells was measured as reported previously (Arai et al., 2002). Membrane aliquots were incubated for 15 min at 25°C with 50 nM [³H]S-AMPA and various concentrations of CX546 in HEPES-buffered saline without potassium thiocyanate. Incubations were terminated by filtration. CX546 increased [³H]AMPA binding to all subunits, the maximal extent of the increase being 30 to 130%, depending on the subunit. Fitting of a sigmoidal curve (Hill slope = 1) to the data points provided an EC₅₀ value for CX546. Drug EC₅₀ values determined in this manner were previously shown for various AMPA receptor modulators to be similar to those obtained in physiological experiments, both with brain AMPA receptors and homomeric receptors (Arai et al., 2000). n represents the number of independent determinations. Values are mean ± S.E.M.