Figure 8.
Pair recording showed that EPSCs evoked by long presynaptic depolarization had smaller amplitude and less slow release in DKO calyces. Calyces and the principal cells of the MNTB were simultaneously voltage clamped at −80 and −60 mV, respectively. The presynaptic calyces were stimulated by long depolarization. Stimulation protocol was −80 to +70 mV for 2 ms, followed by 50 ms at 0 mV and then back to −80 mV. A1, A2, Sample traces for calcium current and EPSC evoked by long depolarization from P9 to P11 WT (A1) and Munc13-2-3 DKO mice (A2). Traces shown from top to bottom are presynaptic calcium current, EPSC. B1, B2, Scatter plot data for calcium current charge integrals (B1) and EPSC amplitudes (B2). The presynaptic calcium current was integrated from its onset of the influx to the end of the depolarization as calcium current charge integral. Each point represents one synapse. Data are shown as mean and SEM. *p < 0.05, Student's unpaired t test. C, Normalized EPSC to the peak amplitude. The black trace is from average of 16 WT calyces, and the blue trace is from average of 18 DKO calyces. Note that DKO calyces had less slow release in the late stimulation. The right panel shows a magnified view of the rise phase of the normalized EPSCs. Note that DKO calyces had a slightly faster rise time than WT calyces.