Modulation of memory processing by glutamic acid receptor agonists and antagonists.

Recent hypotheses suggesting a critical role of glutamate receptors in hippocampal long-term potentiation and memory processing suggested a closer examination of this transmitter's effect on memory processing in an in vivo setting. New pharmacological antagonists allow for a separation and examination of various glutamate receptors and their role in memory processing. Mice were trained on a shock avoidance learning paradigm and injected intracerebroventricularly after training with agonists and antagonists of various classes of glutamate receptors. Retention was tested 1 week after training. N-Methyl-D-aspartate (NMDA) receptor agonists enhanced retention in a dose-dependent manner. The enhancement of retention by the non-NMDA agonist kainic acid and quisqualic acid was dose-dependent. L-Glutamic acid, but not D-glutamic acid, enhanced retention. Both NMDA and non-NMDA receptor antagonists produced dose-dependent impairment of retention for footshock training. Administration of the antagonists 24 h after training did not impair memory retention.