Transient Receptor Potential Ankyrin 1 in Taste Nerve Contributes to the Sense of Sweet Taste in Mice.

Transient receptor potential (TRP) channels play a significant role in taste perception. TRP ankyrin 1 (TRPA1) is present in the afferent sensory neurons and is activated by food-derived ingredients, such as Japanese horseradish, cinnamon, and garlic. The present study aimed to investigate the expression of TRPA1 in taste buds, and determine its functional roles in taste perception using TRPA1-deficient mice. In circumvallate papillae, TRPA1 immunoreactivity colocalised with P2X2 receptor-positive taste nerves but not with type II or III taste cell markers. Behavioural studies showed that TRPA1 deficiency significantly reduced sensitivity to sweet and umami tastes, but not to salty, bitter, and sour tastes, compared to that in wild-type animals. Furthermore, administration of the TRPA1 antagonist HC030031 significantly decreased taste preference to sucrose solution compared to that in the vehicle-treated group in the two-bottle preference tests. TRPA1 deficiency did not affect the structure of circumvallate papillae or the expression of type II or III taste cell and taste nerve markers. Adenosine 5'-O-(3-thio)triphosphate evoked inward currents did not differ between P2X2- and P2X2/TRPA1-expressing human embryonic kidney 293T cells. TRPA1-deficient mice had significantly decreased c-fos expression in the nucleus of the solitary tract in the brain stem following sucrose stimulation than wild-type mice. Taken together, the current study suggested that TRPA1 in the taste nerve contributes to the sense of sweet taste in mice.