Fig. 3.

Spontaneous EPSCs mediated by AMPA receptors. (A) Superimposed records from one fiber reveal the rapid onset and slower, exponential decay of monophasic EPSCs, as well as the variation in rise time. (B) As the postsynaptic membrane potential was varied, averaged EPSCs reversed sign near 0 mV and slowed at more positive potentials. From top to bottom, the holding potentials were +50 mV, +30 mV, 0 mV, −20 mV, −70 mV, and −100 mV. (C) Addition of 100 μM cyclothiazide halved the average decay rate of spontaneous EPSCs, increasing the time constant from 0.65 ± 0.13 ms (n ] 91) to 1.25 ± 0.27 ms (n ] 38). (D) An antagonist of AMPA and kainate receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), reversibly blocked EPSCs at a concentration of 10 μM. (E) Nifedipine, a specific antagonist of L-type Ca²⁺ channels, reversibly blocked EPSCs at a concentration of 50 μM.