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Avoidance of environmental gas irritants mediated by TRPA1

Transient receptor potential ankyrin 1 (TRPA1), a member of the TRP superfamily, is expressed in a subset of sensory neurons such as trigeminal and dorsal root ganglia and implicated as a mediator of nociception evoked by diverse peripheral stimuli including pungent chemicals. We hypothesized that TRPA1 would be involved in detecting environmental chemicals to avoid taking in such a threat. To test our hypothesis, we did place preference test using TRPA1 knockout (KO) mice and age matched wild‐type (WT) mice. The mice were first allowed to freely explore a homemade apparatus that consists of four chambers and the connecting tubes. The number of entry times and the amount of time spent in each chamber were recorded. None of the animals had initial bias for either chamber. Then, each chamber was randomly assigned to a chamber in which a piece of cotton paper soaked with a test solution was placed. We tested a TRPA1 agonist, formaldehyde. During a test period of 20 min, WT mice never tried to enter the chamber with formaldehyde. KO mice entered the chamber without hesitation and even stayed there. This result indicates that WT mice detect and recognize formaldehyde as a dangerous substance via TRPA1.