D-CPP-ENE (SDZ EAA 494), A POTENT AND COMPETITIVE N-METHYL-D-ASPARTATE (NMDA) ANTAGONIST - EFFECT ON SPONTANEOUS ACTIVITY AND NMDA-INDUCED DEPOLARIZATIONS IN THE RAT NEOCORTICAL SLICE PREPARATION, COMPARED WITH OTHER CPP DERIVATIVES AND MK-801

d- and l-enantiomers of the competitive NMDA antagonists CPP and CPP-ene, as well as the non-competitive NMDA antagonist MK-801, inhibited spontaneous activity occurring in slices of rat cerebral cortex exposed to Mg2+-free medium. D-CPP-ene (SDZ EAA 494) was the most active competitive antagonist with a threshold concentration of 10 nM and an ED50 of 39 nM. The inhibitory effects of all competitive antagonists were reversible, whereas reversibility following MK-801 (ED50 = 33 nM) was incomplete and slow. D-CPP-ene was also the most potent competitive antagonist against NMDA-evoked depolarizations, having an apparent pA2 value of 6.8; its action was specific to the NMDA type of excitatory amino acid receptor. © 1990.