DNQX is a competitive, non-NMDA glutamate receptor antagonist (IC50s = 0.5 and 0.1 μM for AMPA and kainate receptors, respectively versus IC50 = 40 μM for NMDA receptors).[1],[2],[3] This compound has been used to specifically target AMPA and kainate receptor responses and thus differentiate from that of NMDA receptors. DNQX does not stimulate a robust long-term potentiation in the hippocampus.[4]

Reference:
[1]. Armstrong, N., and Gouaux, E. Mechanisms for activation and antagonism of an AMPA-sensitive glutamate receptor: Crystal structures of the GluR2 ligand binding core. Neuron 28(1), 165-181 (2000).
[2]. Honoré, T., Davies, S.N., Drejer, J., et al. Quinoxalinediones: Potent competitive non-NMDA glutamate receptor antagonists. Science 241(4866), 701-703 (1988).
[3]. Lee, S.H., Govindaiah, G., and Cox, C.L. Selective excitatory actions of DNQX and CNQX in rat thalamic neurons. J. Neurophysiol. 103(4), 1728-1734 (2010).
[4]. Muller, D., Joly, M., and Lynch, G. Contributions of quisqualate and NMDA receptors to the induction and expression of LTP. Science 242(4886), 1694-1697 (1988).