Figure 3.

RTN stimulation drives active expiration in unanesthetized freely behaving rats. A-D, DIA_EMG, ABD_EMG and flow recordings. A, Selective RTN stimulation. During the laser stimulation, an increase in ventilation is associated with the immediate recruitment of rhythmic ABD_EMG. ABD_EMG was also increased and rhythmic during sustained hypercapnia (A, right; F_ICO₂ = 0.09). B, Magnification of five respiratory cycles (A, dashed outline) during laser stimulation of RTN neurons. ABD_EMG activity is phase-locked in expiration (E). I, Inspiration. C, Selective C1 stimulation. Note the increase in ventilation compared with A, but without increased ABD_EMG. ABD_EMG was increased and rhythmic during hypercapnia (F_ICO₂ = 0.09). D, Magnification of five respiratory cycles (C, dashed outline) during laser stimulation. Note the absence of rhythmic activity in ABD_EMG compared with B. E, Changes in ABD_EMG amplitude (relative to maximum obtained under CO₂) in response to RTN (n = 6) or C1 (n = 5) stimulation. ANOVA two-way for repeated measures: interaction between cell type and stimulation, F_(1,9) = 8.443, p = 0.017; cell type effect, F_(1,9) = 6.380, p = 0.032; stimulation effect, F_(1,9) = 10.04, p = 0.011. Bonferroni's multiple comparisons (resting vs stimulation): RTN, p = 0.003; C1, p > 0.99. F, Absolute number of active expiration events observed during 20 s of stimulation. Mann–Whitney: RTN vs C1, p = 0.004. G, DIA_EMG amplitude in response to RTN (n = 4) or C1 (n = 5) stimulation. ANOVA two-way for repeated measures: interaction between cell type and stimulation, F_(1,2) = 0.926, p = 0.434; cell type effect, F_(1,4) = 0.147, p = 0.720; stimulation effect, F_(1,4) = 76.2, p = 0.0009. Bonferroni multiple comparisons (resting vs stimulation): RTN, p = 0.001; C1, p = 0.002. *p < 0.05 (Bonferroni's multiple comparisons or Mann–Whitney; F).