Figure 7.

Each spike in a FS interneuron burst is driven by a distinct EPSC. A, Multisynaptic current input injected to the soma of the FS interneuron elicits bursts at 35°. Top, Input generated by converting a voltage-clamp response recorded in the same FS interneuron into a current command. Bottom, Burst response of a FS interneuron to the above input. B, Histogram of number of EPSCs that preceded the first spike in a burst (left), the second spike (middle), and the third spike (right) in a burst. Time 0 is the time of the spike. On average, EPSCs precede spikes by 2.06 ± 0.23 ms (n = 8). C, Visualization of a slice under IR-DIC optics where CA3 has been cut off. D, Outer molecular layer stimulation-recruited bursts (top) and multisynaptic currents (bottom) are still present in FS interneuron of a slice that has had CA3 removed (n = 4/4 slices). E, Late EPSCs and spikes in FS interneurons are blocked by type II metabotropic glutamate receceptor agonist. Overlaid 40 ms clips of the current (top) and voltage (bottom) responses of a FS interneuron to a 10 Hz stimulus train delivered to the outer molecular layer in control (Ctrl), 5 μm DCG-IV, and wash show block and recovery of late EPSCs and bursts. F, The probability of bursts is significantly lower in the presence of DCG-IV compared with control and wash conditions (p ≤ 0.01, one-way ANOVA with repeated measures, Dunnett's test, n = 5).