Concurrent deletion of TASK-2 in H81F-Jx99 mice does not further decrease the HCVR or RTN neuron activation. A, Minute ventilation (V_E), tidal volume (V_T), and respiratory frequency (fR) in WT control (HH/++, N = 10, P68–P144), H81F (FF/++, N = 12, P61–P139), TASK-2 deleted (HH/−, N = 9, P61–P214), and double mutant H81F and TASK-2 deleted littermates (FF/−, N = 10, P61–P193) in response to increasing levels of inspired CO₂ (balance O₂). Two-way RM ANOVA analysis: V_E, F_(3,35)= 15.78; p < 0.0001 for genotype, and F_(12,140)= 13.78; p < 0.0001 for CO₂× genotype; V_T, F_(3,35)= 2.802; p = 0.0541 for genotype, and F_(12,140)= 4.337; p < 0.0001 for CO₂× genotype; fR, F_(3,35)= 10.74; p < 0.0001 for genotype, and F_(12,140)= 9.016; p < 0.0001 for CO₂× genotype. P values displayed are from Šídák's multiple-comparison test, for WT (HH/++) vs all other groups. B, Minute ventilation of WT control (HH/++, N = 10), H81F (FF/++, N = 12), TASK-2 deleted (HH/−, N = 9), and double mutant H81F and TASK-2 deleted littermates (FF/−, N = 10) during exposure to the indicated levels of inspired O₂. Two-way RM ANOVA analysis: F_(3,36)= 1.271; p = 0.2988 for genotype, and F_(6,72)= 3.259, p = 0.0068 for genotype × O₂. (C, D) Distribution (left) and total percentage (right) of Fos-immunoreactive GFP–labeled neurons and total number of GFP-expressing (D) neurons throughout the rostrocaudal extent of the RTN in WT control (HH/++, N = 7), H81F (FF/++, N = 11), TASK-2 deleted (HH/−, N = 6), and double mutant H81F and TASK-2 deleted littermates (FF/−, N = 7) after exposure in vivo to 12% CO₂. The total percentage of RTN (GFP⁺) neurons expressing Fos for each group, analyzed by one-way ANOVA, F = 41.79; p < 0.0001; p values displayed are from Tukey's multiple-comparison test.