Figure 5.

Blockade of endogenous GABA_AR activity broadens both EPSPs and the time window for coincidence detection in middle/high-CF neurons. A, SR95531 (20 μm) blocked sIPSPs and hyperpolarized the membrane. The inset shows a short period of the recording at an enlarged timescale. B, SR95531 significantly hyperpolarized the membrane (n = 33) (black and red bars) and increased the input resistance (n = 11) (black and red bars). The same effects were observed when the initial membrane potential under the control conditions was adjusted to a fixed level (−65 mV) with somatic current injections (n = 6) (gray and green bars). C, Left, EPSPs recorded with (red) and without (black) SR95531. Right, EPSPs normalized to their peak showing the time course. D, SR95531 significantly increased both the amplitude and the half-width (the time period at the half-amplitude) of EPSPs (n = 10). E, Experimental paradigm. The two electrical stimuli (Ipsi and Contra) activate the dorsal and the ventral glutamatergic inputs, respectively. The time intervals between the two stimuli were varied to simulate the process of ITD coding. F, Voltage responses to bilateral stimulations with and without SR95531. Time intervals between the two stimulations are indicated on bottom of the panel. The numerical on the top right of each set of traces indicates the spike probability. G, Normalized firing probabilities as a function of time intervals (n = 9). H, SR95531 significantly increased the time window of coincidence detection (n = 9).