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. 2022 Oct 12;42(41):7690–7706. doi: 10.1523/JNEUROSCI.0570-22.2022

Figure 6.

Figure 6.

Spike-triggered hyperpolarizations regulate the duration of persistent discharges. A, Diagram of microcontroller-based responsive feedback system used to augment endogenous spike AHPs. The analog output of the microcontroller produces exponentially decaying hyperpolarizing transients that are added to the step generator to generate the patch-clamp amplifier current input. Analog signal summation (“Sum”) was mediated by a two-channel unity gain buffer amplifier. A digital control signal (data not shown) disabled the responsive feedback system during the step stimulus. B, Persistent discharges triggered by depolarizing current steps in an L5 pyramidal cell alone (Control) and spike AHPs augmented via responsive feedback (bottom three panels with orange current traces). Grading the amplitude AP-linked hyperpolarizations modulated the duration of self-terminating discharges (maximal injected current varied between −50 and −150 pA). C, Two different randomly timed trains of similar hyperpolarizing transients failed to terminate persistent firing (middle panels with green current traces). Control bistable response (top panel) and self-terminating response with AP-linked feedback hyperpolarizations (same −50 pA peak current amplitude; bottom panel) recorded from the same neuron. D, Summary of probability of self-terminating activity with AP-linked (orange) and randomly timed hyperpolarizations (green). All decay τ, 1 s: ***p = 2e-7; T = 14.10, df = 5; paired t test. E, Summary of reduction in the duration of persistent activity by different amplitude AP-linked hyperpolarizations (all decay τ, 1 s). All comparisons: **p < 0.002, T > 4.587, df = 5; paired t tests. Analysis restricted to self-terminating trials. F, Survival plots of duration of self-terminating discharges with different responsive feedback current injection maximal amplitudes (−50 vs −100 pA: p < 0.0005, T = 0.498; −50 vs −150 pA: p < 3.33e-09, T = 0.755; −100 vs −150 pA: p < 3e-05, T = 0.562; K-S tests). All recordings with CCh and ML297 are shown. Horizontal orange bars indicate times when the responsive feedback system was operational.