CNQX

CNQX, or 6-cyano-7-nitroquinoxaline-2,3-dione, is a synthetic heteroaromatic compound used as a pharmacological tool in neuroscience. It functions as a competitive antagonist of non-NMDA glutamate receptors, with a primary affinity for AMPA receptors and a lesser but notable activity at kainate receptors. By binding to the ligand-binding domains of these ionotropic receptors, CNQX blocks glutamate from activating the channels and reduces excitatory synaptic transmission.

In practice, CNQX is employed to dissect glutamatergic signaling in brain tissue and cultured neurons. It is commonly applied in electrophysiological experiments to suppress AMPA- and kainate-mediated currents, thereby allowing researchers to isolate NMDA receptor–dependent responses or to study the role of non-NMDA receptors in synaptic plasticity and excitotoxicity. Effective concentrations are typically in the micromolar range and depend on the experimental system.

CNQX shows selectivity favoring AMPA receptors over kainate receptors, though it can inhibit kainate receptors at higher concentrations. It is part of a family of non-NMDA receptor antagonists used in research, including related compounds such as DNQX and NBQX, which provide alternative profiles of receptor blockade. CNQX is not approved for clinical use and is used exclusively as a research reagent.

Overall, CNQX remains a standard tool for probing non-NMDA glutamatergic transmission in the central nervous system, contributing to studies of synaptic physiology, neuropharmacology, and models of neurological disease. Researchers select CNQX based on the desired level of AMPA versus kainate receptor blockade and the specific experimental design.