Fig. 6.
EPSCs and excitatory postsynaptic potentials (EPSPs) recorded at the IHC afferent synapse. A–K: whole cell recording from an afferent dendrite in the presence of 1 μM TTX showing EPSCs (A, B) (holding potential −94 mV) and EPSPs (E, F). B and F: overlaid representative traces of monophasic EPSCs and EPSPs on an expanded timescale. C, D, G, and H: 10–90% rise time (rise) or decay time constants (τdecay) plotted against the EPSC or EPSP amplitude. Rise and τdecay for EPSCs were 0.33 ± 0.14 and 1.24 ± 0.20 ms (324 EPSCs analyzed). Rise and τdecay for EPSPs were 0.96 ± 0.12 and 3.81 ± 0.36 ms (241 EPSPs analyzed). EPSP waveforms remained relatively invariable over the wide range of EPSP amplitudes. I–K: EPSP amplitude distributions (bin size 1 mV) from 3 afferent dendrite recordings. Median EPSP amplitudes were 2.3, 2.4, and 13.8 mV and resting membrane potentials were −75, −56, and −68 mV, respectively. The number of events analyzed is indicated in each panel. L–N: whole cell current-clamp recording in the absence of TTX. A mixture of EPSPs and spikes was observed. M: overlaid representative traces of spikes on an expanded timescale. Spike threshold (arrow) was −47 mV for this recording. N: amplitude distribution (bin size 1 mV). A wide gap in amplitude histogram distinguishes spikes from EPSPs.