Figure 7.

Synaptic depression at different extracellular calcium concentrations. A, Synaptic currents recorded in principal cells in brain slices during and following a 400 ms, 500 Hz stimulus train at three different calcium concentrations: 1.2 (green), 1.5 (red), and 2 mm (black). Time axis indicates start of individual EPSCs relative to the end of the stimulus train. B, Time course of synaptic depression and recovery from synaptic depression of EPSCs during the 500 Hz train. Solid lines show the fit of the recovery phase with the sum of two exponential functions (Table S2, available at www.jneurosci.org as supplemental material). C, As B, except amplitudes have been divided by the average amplitude of the first EPSC before averaging across experiments. D, As A, but showing first derivative of current-clamp recording. Peak amplitude of the iEPSP′ is marked with a small blue cross. E, Time course of synaptic depression and recovery from synaptic depression of the rate of rise of the EPSPs during the 500 Hz train. Solid lines show the fit of the recovery phase with the sum of two exponential functions (Table S2, available at www.jneurosci.org as supplemental material). F, As E, except potentials have been normalized to the first one.