CNQX (FG9065) is a potent AMPA/kainate receptor antagonist. In Vitro: In rat hippocampal slices bathed in Mg²⁺-free medium, 10 μM CNQX reversibly blocks responses to a-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), quisqualate and kainate but not NMDA^[1]. Superfusion of hippocampal slices with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 2-5 μM) reversibly blocks the Schaffer collateral and mossy fibre excitatory postsynaptic potential (EPSP), while sparing the fast and slow GABA-mediated inhibition^[2]. CNQX (1-5 μM) produces a selective and dose-dependent reduction in the amplitude of the monosynaptic component of the DR-VRR recorded from lumbar spinal segments^[3]. CNQX-mediated depolarizations are mediated by AMPAR but not kainate receptors in TRN neurons^[4]. In Vivo: The bilateral infusion of CNQX (0.5 or 1.25 μg) into the amygdala or dorsal hippocampus 10 min prior to a retention test partially blocks the expression of stepdown inhibitory avoidance in rats 24 h after training. CNQX causes a complete blockade at a dose of 0.5 μg^[5].