Figure 7.

Developmental in vivo changes in STP during electrical stimulation following cochlear ablation. A, Illustration of electrically evoked complex waveforms from a P6 rat showing synaptic facilitation at short intervals (left), depression at intermediate intervals leading to a postsynaptic failure (middle), and recovery from depression at long intervals (right) animal. Symbols above the waveforms refer to events shown in B. B, Dependence of eEPSP size on stimulus interval. Same in vivo-like protocol was used as in Figure 6. Red dots show individual suprathreshold eEPSP amplitudes, purple dots show subthreshold eEPSP amplitudes, and individual squares, triangles, and inverted triangles refer to examples shown in A. Green symbols show binned averages with SD, and black circles indicate fit with an STP model with both facilitation and depression. Fit parameters were as follows: amplitude 0.5 mV; 130% facilitation per AP, decaying with a time constant of 97 ms; and 29% depression per AP, decaying with a time constant of 725 ms. The fit could account for 50% of the variance in the eEPSP amplitudes. C, As in B, except that the recording was from a P28 animal. Fit parameters were as follows: amplitude 0.8 mV; 64% facilitation per AP, decaying with a time constant of 6.8 ms; there was no depression. The fit could account for 15% of the variance in the eEPSP amplitudes.