Average ΔF/F0 iGluSnFR traces in response to 10-ms-long step depolarizations from the holding potential (-87 mV) to a voltage within the physiologically relevant range of receptor potentials: from -62 mV to -22 mV (applied in pseudo-randomized order, step-size 5 mV, perforated patch-clamp, 1.3 mM [Ca2+]e, n = 29 boutons, N = 11 IHCs from 9 mice). Shaded areas show ± SD. 