Figure 3.

The recovery of GABA_A receptors from desensitization depends on the duration of GABA application. GABA (10 mm) was applied to outside-out patches excised from Mb-type bipolar cell terminals after a whole-cell recording. The current responses consisted of a nondesensitizing GABA_C component, and a fully desensitizing GABA_A component (Hull et al., 2006) A, A preapplication of GABA for 5 s (as indicated by the black bar) was used to fully desensitize GABA_A receptors, and then GABA (10 mm) was applied for 2 s (as indicated by gray arrows) to induce current after a variable interpulse interval. The longer the interval, the more the peak of the current response recovered. B, The recovery time course of peak current from A was constructed and fitted with a single exponential equation (τ = 11.9 s; gray trace). C, In this example, for a 100 ms GABA preapplication, GABA_A current recovered 73.6% at 10 s (gray trace; the arrow indicates the peak of the red trace) of the preapplication control (black). D, For 5 ms GABA preapplications, the peak of the current response recovered completely within 2 s. Error bars indicate SE.