NMDA ANTAGONISTS POTENTIATE SCOPOLAMINE-INDUCED AMNESIC EFFECT

The effects of N-methyl-D-aspartate NMDA receptor antagonists on scopo lamine-induced amnesia and on delay-interposed short-term memory perfo rmance were investigated using an 8-arm radial maze in rats. Scopolami ne, a muscarinic antagonist, deteriorated the radial maze performance, while MK-801, an NMDA receptor channel blocker and CGS-19755, a compe titive NMDA receptor antagonist, showed no obstruction to the spatial cognition in the non-delayed maze task. MK-801 (0.01-0.03 mg/kg, i.v.) and CGS-19755 (1-10 mg/kg, i.v.) significantly augmented scopolamine- induced deficit in the non-delayed maze task and impaired the short-te rm memory in the 5-min delay-interposed task. These results suggest th at NMDA antagonists have a negative action on short-term memory and th at the interaction between the NMDA and the central muscarinic system plays a role in modulating the cognitive function.