Figure 11.

GABA current was potentiated by an epileptiform burst. A, Membrane potential of a hippocampal neuron in the presence of 4-aminopyridine (100 μm). Bursts of high-frequency action potentials occur spontaneously. Data enclosed in the dashed box were used to create the stimulus waveform used in voltage-clamp experiments. B, Responses to GABA (1 or 10 μm) at a holding potential of −60 mV with and without epileptiform depolarization. Current amplitude was measured 0.2 and 2 s after the stimulus (see dashed lines in right panel) and compared with control currents at the same time points. C, Mean potentiation of GABA current by epileptiform depolarization at 0.2 and 2 s after repolarization (n = 4). D, Tonic current before and after epileptiform depolarization. Illustrated currents are the average of three trials from this cell recorded in presence of 0.3 μm exogenous GABA. E, Normalized tonic current amplitude from experiment in D. F, Mean potentiation of tonic current by epileptiform depolarization (n = 7). Error bars represent SEM.