Molecular cloning and characterization of dog TRPA1 and AITC stimulate the gastrointestinal motility through TRPA1 in conscious dogs

Transient receptor potential ankyrin1 (TRPA1) is a non-selective cation channel activated by cold stimuli under 17 °C, mechanosensation, and pungent irritants such as allyl isothiocyanates (AITC) and cinnamaldehyde (CA). In this study, we cloned the dog orthologue of TRPA1 for the first time and induced its heterologous expression in HEK293 cells to investigate its functional properties using a fluorescence imaging plate reader-based Ca2+ influx assay. Moreover, we examined the effect of AITC on gastrointestinal motility in dogs. At the amino acid level, the sequence of dog TRPA1 was 82–83% identical to that of human, mouse, and rat orthologues. TRPA1 is strongly expressed in the brain, cerebellum, stomach, pancreas, and small and large intestine of dogs. Like other mammalian orthologues, TRPA1 agonists, including AITC, CA, allicin, and diallyl disulfide, evoked a concentration-dependent increase in intracellular Ca2+ influx in dog TRPA1-expressing cells. AITC stimulated gastric antrum and jejunum motility and induced the occurrence of giant migrating contractions in the colon of fasted dogs. The effects of AITC were inhibited by ruthenium red, a TRPA1 antagonist. These results indicate that AITC stimulated the gastrointestinal motility through TRPA1 in conscious dogs.