Figure 3.

Properties and pharmacology of the EPSC. A, Postsynaptic current responses elicited by giant terminal stimulation at different membrane potentials. The fast component (1.8 ms after stimulus, gray bar, C) and slow component (10 ms after stimulus, gray bar, E) are highlighted. V _m = −70, −50, −30, −10, +10, +30, +50, and +70 mV. The stimulation artifact is marked with an arrow. B, Fast inward current at −70 mV was insensitive to the NMDA receptor antagonist APV (50 μm) but was nearly completely blocked by the AMPA receptor antagonist CNQX (10 μm). C, Current–voltage relationship of the fast EPSC component in the presence of glutamate receptor blockers (n = 4). The pipette contained 100 μm spermine to maintain voltage-dependent block of Ca²⁺-permeable AMPA receptors. The current-voltage relationship is inwardly rectifying. Rectification index equals the slope at +20 to +70 mV divided by slope at −120 to +10 mV. D, As in B, but at +70 mV. Slow outward but not AMPAR current was blocked by APV. E, As in C but the current–voltage relationship of the slow EPSC component (n = 4).