Figure 3. EPSCs in cochlear afferents.

A, excitatory postsynaptic currents recorded from afferent boutons at their point of contact with the inner hair cell. Membrane potential –94 mV. B, cumulative EPSC amplitude plots constructed from 3 different afferent fibres with different mean rates of release. Fibre no. 4 was measured in ‘normal’ conditions where membrane potentials are –60 mV on average. Fibre no. 2 was bathed in 40 mm K⁺ saline, which depolarized hair cells to ∼–35 mV. Fibre no. 8 had ‘bursting’ EPSCs whose timing suggested that they were produced by calcium action potentials in the neonatal hair cell. These exemplar recordings illustrate the fact that release probability did not correlate with EPSC amplitude distribution. (From Glowatzki & Fuchs, 2002; with permission; ©Nature Publishing Group, http:///www.nature.com).