Abstract: Using radioligand binding assay, the effects of (-), (+) clausenamide on N-methyl-D-asparate(NMDA) receptor were studied in synaptic membrane, hippocampus and cerebral cortex in rats. The Bmax and K_D values of NMDA receptor in mouse brain were measured with Scatchard plot method. Results showed that there was no specific binding of (-), (+) clausenamide to NMDA-receptor. However, higher Bmax values were observed in (-) clausenamide-treated rats than the control group, but no effect on K_D value. (+) Clausenamide treatment showed no effect on Bmax and K_D values. The findings suggest that the pharmacologic actions of clausenamide depends on its chirality. Up regulation of NMDA-receptor induced by (-) clausenamide is helpful to elucidate its nootropic mechanism.