Figure 6. Increased tonic inhibitory current during spontaneous bursts of sIPSCs.

A, whole-cell voltage-clamp recording from a molecular layer interneuron in the presence of 3 mm kynurenic acid and 5 μm GABA (V_h=−70 mV) showing a spontaneous burst of sIPSCs (•). Lower panel shows expanded 5 s segments from the burst (•, 52 Hz) and control (○, 9 Hz) conditions. The dashed line indicates the baseline current in the control condition. B, simulated traces using the recorded parameters (frequency, peak amplitude, 10–90% rise time, τ_w and baseline noise) from the experimental condition. The dashed line indicates a baseline current of 0 pA. C, left panel: Gaussian fits to all-points histograms of the simulated traces using the parameters obtained from the experimental condition at 1-times and 1.5-times the maximum experimentally obtained event frequency during the burst. Shifts in baseline currents are as follows during the respective sIPSC frequencies: 10.4 Hz (−1.31 pA), 50.9 Hz (−2.69 pA) and at 75.7 Hz (−4.46 pA). Right panel: the difference in the tonic current measured in the experiment between the control condition and the spontaneous burst. GABA spillover must account for 13.4 pA of the increase in tonic current (16.1 pA − 2.69 pA).