Figure 2. The amplitude of miniature excitatory postsynaptic currents (mEPSCs) increased after dialyzing cones with 40 mM glutamate. A: This shows the postsynaptic current recorded from a horizontal cell before and after depolarization of the presynaptic cone to −30 mV. Letters above the trace identify the short segments that are reproduced at a higher timescale in panels B and C. B: Sample of baseline mEPSCs recorded from a light-adapted horizontal cell before stimulation. Individual mEPSCs are indicated by arrows. C: Sample of mEPSCs obtained while depolarizing the presynaptic cone to −30 mV. D: Cumulative amplitude histograms of mEPSCs recorded during baseline conditions (solid line, n=336 events) and during a step to −30 mV (dashed line, n=360 events) from the cell pair shown in the previous panels. In this example, the mean amplitude increased from 7.11±0.24 pA to 7.91±0.24 pA, following application of the depolarizing step. The frequency of mEPSCs increased from 65.7 to 72.0 Hz.