Figure 3. Lack of NaOCl-induced Ca²⁺ influx in sensory neurons and respiratory insensitivity to NaOCl aerosol in Trpa1^–/– mice.

(A) Responses of cultured DRG neurons from littermate Trpa1^+/+ and Trpa1^–/– mice to NaOCl (24 ppm) followed by 5 μM capsaicin, as measured by Fura-2 imaging. Trpa1^–/– neurons showed no [Ca²⁺]_i increase after NaOCl exposure, but were activated by capsaicin. Pseudocolors denote 0–3 μM [Ca²⁺]_i. (B) Activation of Ca²⁺ influx into DRG neurons plotted against time. Average [Ca²⁺]_i concentration of neurons activated by application of NaOCl followed by mustard oil, capsaicin, and 65 mM KCl. Thick and thin lines denote mean and ± SEM, respectively. Neurons (n = 300 [Trpa1^+/+]; 263 [Trpa1^–/–]) cultured from 4 mice per group were analyzed at ×10 magnification. (C) Effects of exposure to NaOCl aerosol on respiratory frequencies, as measured by unrestrained plethysmography. Mice were exposed to vehicle aerosol (10 min), room air flush (2 min), NaOCl aerosol (15 min), and then air (8 min). Values denote percentage of baseline (initial vehicle exposure). Respiratory frequency was slightly affected in Trpa1^–/– mice, but dramatically declined in Trpa1^+/+ mice during NaOCl exposure and when NaOCl aerosol was replaced by air. Error bars denote SEM. P < 0.00005 between groups; P < 0.000001 over time (repeated-measures ANOVA). n = 11 per group. (D) EEP duration during exposure to NaOCl aerosol. Data were collected from the experiment described in C. Unlike Trpa1^–/– mice, Trpa1^+/+ mice responded to NaOCl aerosol with an approximately 3-fold increase in EEP duration, which remained elevated 8 min after the end of NaOCl exposure. P < 0.000001 between groups, over time, and for the interaction of genotype and time (repeated-measures ANOVA). Single asterisks denote significant differences (Bonferroni post-hoc analysis; α = 0.05) for individual time points.