Blockade of excitatory synaptic transmission by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in the hippocampus in vitro.

Superfusion of hippocampal slices with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 2-5 microM) reversibly blocked the Schaffer collateral and mossy fibre excitatory postsynaptic potential (EPSP), while sparing the fast and slow gamma-aminobutyric acid (GABA)-mediated inhibition. Membrane potential, input resistance and spike accommodation were not altered. Inward currents induced by quisqualate were reduced to a greater extent by CNQX than those induced by kainate or N-methyl-D-aspartate. We suggest that CNQX may be a useful antagonist to study excitatory amino acid-mediated synaptic transmission.