Figure 1.
Synaptic responses evoked by electrical stimulation of the MOC efferent fibers in mouse OHCs. A, Schematic representation of the experimental setup. OHCs from the first row were recorded with a patch pipette while electrical shocks were delivered to the MOC fibers through an extracellular bipolar theta glass pipette positioned ∼10–20 μm below the IHCs. Scale bar, 10 μm. B, Representative trace obtained in an OHC in response to two single electrical shocks (arrows). The figure shows one eIPSC and one sIPSC, respectively, and also a failure of response upon nerve stimulation. C, Preventing the generation of axonal action potentials with 1 μm TTX caused a reversible block of the postsynaptic responses evoked by four shocks at 250 Hz. D, Representative traces of single-shock-evoked IPSCs in OHCs held at membrane voltages ranging from −40 to −100 mV. E, IPSPs obtained in the same cell in the current-clamp configuration. The holding (Vh) and the membrane (Vm) voltages are indicated in D and E, respectively. Note that, at Vh negative to −80 mV, IPSCs are completely inward, while positive to −80 mV a slow outward current develops in addition to the fast inward component (D). These outward currents are mirrored by hyperpolarizing responses in the current-clamp configuration (E). In F, more detailed traces of the biphasic response are shown in the voltage-clamp configuration at a Vh of −70 mV (top panel) and in the current-clamp configuration (bottom panel) starting from a resting potential of approximately −73 mV. The arrows indicate the fast inward/depolarizing phase of the two components of the synaptic response. G, I–V curve obtained plotting peak IPSCs amplitudes versus Vh in the cell illustrated in D.