Dextrorphan blocks long- but not short-term memory in a passive avoidance task in rats.
In the present study a mixed sigma and PCP (phencyclidine) site ligand, dextrorphan (22 mg/kg), blocked long- but not short-term memory in a passive avoidance task. This effect was not accompanied by any behavioral alterations that could interfere with passive avoidance performance. The action of dextrorphan was shared by a selective NMDA (N-methyl-D-aspartate) receptor antagonist, MK-801 (5-methyl-10,11-dihydro-5H-dibenzocyclohepten-5,10-imine maleate, 0.1 mg/kg). The results suggest that dextrorphan affects long-term memory, probably via blockade of NMDA receptors.
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