Figure 3. Synaptic GlyRs mediate phasic IPSCs. A, Low-frequency IPSCs recorded in the absence (Control) or presence of 1 μm ICS 205.930, as indicated. Insets emphasize fits of three-exponential curves (gray) to early and late phases of IPSC decay [fitted time constants (relative amplitudes) are 2.2 ms (94.9%), 23.6 ms (3.3%), and 114.2 ms (1.8%) for control and 3.0 ms (94.9%), 17.8 ms (3.6%), and 109.3 ms (1.5%) for ICS 205.930]. B, Values of the time constants (left bar graph) and relative magnitudes (right bar graph) of each component in the fitted curves in control and ICS 205.930 for three-exponential fits to decay of low-frequency IPSCs. C, Examples of glycinergic mIPSCs recorded from an MNTB principal cell in the absence (Control) or presence of ICS 205.930 (20 mIPSCs are shown for each treatment). D, Superimposed traces represent averages of 594 events (Control, black) or 560 events (ICS 205.930, gray) obtained from the same cell shown in C. Note that the drug increased both the maximal amplitude and the decay time of mIPSCs. E, Normalized cumulative distributions of maximal mIPSC amplitudes obtained from all eight cells analyzed. In each cell, the data were collected from 10 min long recording periods before (black; 3199 events), during (solid gray; 2829 events), or 10 min after (broken gray; 2923 events) bath application of ICS 205.930. The drug caused a significant shift of mIPSC amplitudes toward higher values (p < 0.001, Kolmogorov–Smirnov test). F, The traces show trains of 50 IPSCs stimulated at 100 Hz in the absence (Control, black trace) or presence of 1 μm ICS 205.930 (gray trace). The arrow marks the decay after the train in ICS 205.930 and the dashed lines indicate levels of the tonic IPSC. G, The plot shows the magnitude of the effects of ICS 205.930 on trains of IPSCs. Data points represent average values of peaks of phasic IPSCs (circles, left y-axis) or currents just preceding the phasic IPSCs (squares, right y-axis) obtained from 10 trains recorded every 20 s in the absence (open symbols) or presence of the drug (filled symbols). The data are from the same cell as in F. H, Bar graph summarizes the effects of ICS 205.930 on trains of IPSCs. P denotes the peak of the phasic IPSC measured from the current level just preceding the stimulus artifact. τSingle and τTrain represent amplitude-weighted mean time constants of decays of single low-frequency IPSCs or trains of IPSCs. The data are collected from 8 to 14 cells. *p < 0.05 or **p < 0.01 (paired t test).