Figure 6. Reduced respiratory and nociceptive sensitivity of Trpa1^–/– mice to H₂O₂.

(A) Change in respiratory frequency during aerosol exposure to PBS and 3% H₂O₂, as measured by unrestrained plethysmography. Mice were exposed to vehicle aerosol (10 min), room air flush (2 min), H₂O₂ aerosol (15 min), and then air (8 min). Values denote percent baseline (initial vehicle exposure). Both groups showed a significant decrease in respiratory frequency during H₂O₂ exposure compared with vehicle; however, the reduction in Trpa1^+/+ mice was significantly greater. P < 0.005 between groups; P < 0.000001 over time (repeated-measures ANOVA). (B) Changes in respiratory frequency after exposure to H₂O₂ (2–15 min) and air (8 min) as in A. Values denote percent baseline (initial vehicle exposure). (C) Changes in EEP duration during exposure to H₂O₂ aerosol as in A. P < 0.001 between groups; P < 0.000001 over time (repeated-measures ANOVA). Single asterisks denote significant differences (Bonferroni post-hoc analysis; α = 0.05) for individual time points in A and C. (D) Change in EEP over duration of exposure to vehicle (2–10 min), H₂O₂ (2–15 min), and air (8 min). (E) Nocifensive responses following paw injection of 25 μl of 0.1% H₂O₂ solution (32 mM). The number of nocifensive responses (paw flicks, licks, and lifts) was averaged in 1-min intervals. (F) Pain responses accumulated over a 5-min period following injection of H₂O₂ as in E. (A–D) n = 14 per group. (E and F) n = 12 (Trpa1^+/+), 11 (Trpa1^–/–). Error bars denote SEM. **P < 0.01; ***P < 0.001 (ANOVA).