6,7-Dinitro-quinoxaline-2,3-dion and 6-nitro,7-cyano-quinoxaline-2,3-dion antagonise responses to NMDA in the rat spinal cord via an action at the strychnine-insensitive glycine receptor.

6,7-Dinitro-quinoxaline-2,3-dion (DNQX) and 6-nitro,7-cyano-quinoxaline-2,3-dion (CNQX) produce an unsurmountable antagonism of responses to N-methyl-D-aspartate (NMDA) in the baby rat hemisected spinal cord. These effects of DNQX and CNQX can be prevented in a dose-dependent manner by co-superfusion with D-serine or glycine (in the presence of strychnine). The results suggest that the unsurmountable blockade of NMDA responses by DNQX and CNQX reflects an antagonist effect mediated at the allosterically linked strychnine-insensitive glycine receptor.