Modulation of NMDA receptor by huperzine A in rat cerebral cortex.

AIM To investigate the effects of huperzine A (Hup A) on NMDA receptors in rat cerebral cortex. METHODS 1) The effect of hup A on NMDA-induced current was studied in acutely dissociated rat hippocampal pyramidal neurons using whole-cell recording. 2) The effect of Hup A on NMDA receptor binding was assessed using [3H] dizocilpine (Diz) binding assay in synaptic membrane preparation of rat cerebral cortex. RESULTS 1) Hup A reversibly inhibited NMDA-induced current in a concentration-dependent manner with IC50 of 45.4 mumol.L-1. 2) Hup A inhibited the specific binding of [3H]MK-801 to extensively washed synaptic membrane of rat cerebral cortex in a concentration-dependent manner with IC50 of 0.5 (0.1-1.9) mumol.L-1 (n = 4). 3) L-Glutamate 10 mumol.L-1 markedly increased [3H] MK-801 binding. In the presence of L-glutamate, Hup A 0.001-0.1 mumol.L-1 caused a further increase of the binding, whereas Hup A 1-300 mumol.L-1 inhibited the binding in a concentration-dependent manner with IC50 of 12.3 (5.8-26.3) mumol.L-1 (n = 5). CONCLUSION Hup A acted as an antagonist of NMDA receptor in cerebral cortex in addition to its inhibitory effect on acetylcholinesterase.