Table 1.

In vitro binding affinity of ZK200775 to glutamate receptors in rat cortical membranes

Glutamate receptor ligands	3H-AMPA	3H-CNQX	3H-KA	3H-CPP	3H-TCP	3H-DCKA	3H-glycine
IC50, μM	0.12 ± 0.09	0.032 ± 0.008	2.5 ± 0.2	2.8 ± 0.35	11 ± 2.1	2.8 ± 0.5	5.15 ± 0.21

Rat (Wistar; Møllegaard, Lille Skendsved, Denmark) frontoparietal cortex was homogenized in buffer containing 30 mM Tris⋅HCl, 2.5 mM CaCl₂ (pH 7.1). The homogenate was centrifuged at 40,000 times g for 15 min, and the pellet was washed (3×) and suspended in buffer. Incubations were performed in triplicate at 0°C for 30 min and bound radioactivity separated by filtration through Whatman GF/C glass fiber filters. Nonspecific binding was defined by the addition of 680 μM l-glutamate, except for TCP binding, for which 3.5 μM phencyclidine was used. For glycine binding, the membranes were washed with buffer containing 5 mM Hepes/Tris and 2.5 mM MgCl₂ (pH 7.1) supplemented with 0.08% Triton X-100. Nonspecific binding was defined by 100 μM d-serine, and membrane-bound tracer was separated by centrifugation. ZK200775 was dissolved in ethanol and added in at least four concentrations. The IC₅₀ values were calculated by nonlinear regression analysis. Shown are means ± SEM of three determinations.