NMDA receptor-independent epileptiform activity induced by magnesium-free solution in rat amygdala neurons is blocked by CNQX.

The effect of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a specific non-N-methyl-D-aspartate (non-NMDA) receptor antagonist, on NMDA-independent epileptiform activity induced by Mg2(+)-free medium was studied in rat basolateral amygdala (BLA) neurons using intracellular recording techniques. Twenty to 30 min after switching to Mg2(+)-free medium, spontaneous and evoked epileptiform activity were observed in 16 out of 18 amygdala slices. Superfusion of D-2-amino-5-phosphonovalerate (D-APV), a selective NMDA receptor antagonist, reduced the duration of epileptiform activity by an average of 83%. However, there was a residual depolarizing component which remained in the presence of D-APV. This D-APV-resistant component could be completely blocked by CNQX suggesting that it is mediated by non-NMDA receptors.