CNQX infused into rat hippocampus or amygdala disrupts the expression of memory of two different tasks.

The bilateral infusion of CNQX (0.5 or 1.25 micrograms) into the amygdala or dorsal hippocampus 10 min prior to a retention test partially blocked the expression of stepdown inhibitory avoidance in rats 24 h after training. When infused into both the amygdala and the hippocampus at a dose of 0.5 microgram. CNQX caused a complete blockade of the expression of that task. Retention test performance recovered 2 h after the infusions. In rats trained for habituation to a novel environment and tested 24 h later, pretest intrahippocampal CNQX (0.5 microgram) blocked the expression of retention at a dose of 0.5 microgram, and intra-amygdala CNQX (0.5 or 1.25 micrograms) had no effect. The data suggest that, up to at least 1 day after training, memory of the avoidance task depends on glutamate acting on non-NMDA receptors in both the hippocampus and the amygdala, whereas memory of the habituation task depends on non-NMDA receptor activity in the hippocampus but not the amygdala.