Figure 6.

DCN firing bidirectionally adapts to increases and decreases in depolarization over seconds. A, Top, A three-step depolarizing current injection protocol delivered to a DCN cell, starting with an initial 200 pA depolarization for 25 s, followed by a step to 400 pA for 30 s, and then a 200 pA depolarization for 60 s. Middle, Voltage response during a current-clamp recording from a DCN neuron. Bottom, Instantaneous firing response. B, Average instantaneous firing frequency evoked by the three-step current injection protocol. N = 7 cells (5 animals). C, Summary data for the steady-state firing at the ends of the initial depolarization, for the 400 pA step, and for the 60 s recovery. Statistical significance among steady-state firing during initial, step, and recovery periods was assessed by one-way ANOVA and found to be statistically insignificant at a significance level of 0.05. D, Summary data for the decay times to reach steady state for the initial current injection (t_decay1), and for the 400 pA step (t_decay2). Decay times were determined from an exponential fit to the instantaneous firing frequency during the indicated period. In all cases, the spiking stopped when the depolarization was decreased from 400 to 200 pA, and t_firing values are summarized for each cell. Statistical significance between steady-state firing during initial, step, and recovery periods was assessed by one-way ANOVA. The only statistically significant comparison was the time taken to resume firing (t_firing) and the time to reach steady state for the initial current injection (t_decay1; p = 0.025).