Fig. 5.

Phasic inhibition, but not excitation, drives high preBötC burst frequencies. a Representative inspiratory neuron and preBötC population recording during bilateral light stimulation specifically during the expiratory phase in a Dbx1-ChR2 rhythmic brainstem slice. b Representative inspiratory neuron and preBötC population activity during threshold-triggered bilateral light stimulation specifically during the inspiratory phase in a Vgat-ChR2 slice. c Average changes in frequency in Vgat-ChR2 slices during unilateral and bilateral preBötC stimulation during inspiration (n = 8) and expiration (n = 6) compared to Dbx1-ChR2 stimulation during inspiration (n = 5) and expiration (n = 5; one-way ANOVA and Bonferonni’s multiple comparisons test; *p < 0.001). d Intracellular recording of a Vgat− neuron and preBötC population activity during brief light pulses (200 ms) in a Vgat-ChR2 slice. Note that rebound spiking is reduced during the refractory period. Quantified probability of evoking a population burst via postinhibitory rebound relative to the time of light stimulation following an endogenous burst (0.5 s bins; n = 7 slices, ~100–150 trials/slice; mean ± s.e.m.) compared to the probability of evoked bursts during Dbx1 stimulation (data shown in Fig. 2b), demonstrating similar refractory periods