FIGURE 5.

Individual and grouped data showing the age‐related differences between Tph2 ^−/− and Tph2 ^+/+ mice one the baseline minute ventilation (V _E) (a) V _E at 8% of inspired CO₂ (b) and hypercapnic ventilatory response (HCVR) (c). Younger—Tph2 ^+/+ (n = 7), Tph2 ^−/− (n = 5); Older – Tph2 ^+/+ (n = 6), Tph2 ^−/− (n = 6). Tph, tryptophan hydroxylase. *p < 0.05—effect of genotype using two‐way ANOVA. ##p < 0.01 effect of age using two‐way ANOVA. ‡‡p < 0.01 Tukey's post hoc test in comparison with younger Tph2 ^+/+ mice and older Tph2 ^−/ mice