Effects of phorbol ester on NMDA receptor activation and suppression. Pretreatment of hippocampal slices with PMA (1 μM, a PKC activator) potentiating NMDA-induced field potentials (a, b) and prevented ketamine (a, 10 μM)- or D-APV (b, 50 μM)-evoked NMDA receptor blockade. Pretreatment of hippocampal slices with 4α-PDD (1 μM, inactive phorbol ester) did not affect NMDA-elicited field potentials (c, d) and ketamine (c, 10 μM)- or D-APV (d, 50 μM)-induced NMDA receptor blockade. All values are expressed as the mean ± S.E.M. (n = 6). Data were statistically analyzed by one-way ANOVA followed by a Student-Newman-Keuls post-hoc test. #p < 0.05 as compared with the NMDA groups. *p < 0.05 as compared with the NMDA plus ketamine or D-APV groups.