Effect of PDC on the NMDA receptor-mediated current in an isolated spiking neuron. A, A 100 msec puff (top) of glutamate (200 μm) evoked an inward current in an isolated spiking neuron voltage-clamped at −40 mV. Both the superfusate and the puff pipette solution included 5 μm NBQX, 10 μm glycine, and 10 μm strychnine. B, Bath application of PDC (200 μm) reduced the amplitude of the glutamate-induced current. C, The suppressive effect of PDC reversed after washout.