Fig. 3

Effects of borneol, 2-methylisoborneol, fenchyl alcohol, and norcamphor on menthol-induced cytosolic Ca²⁺ increases in HEK293T cells expressing hTRPA1. Fura-2 ratio changes due to menthol (1 mM) application in the presence and absence of borneol (1 mM, a), 2-methylisoborneol (1 mM, b), fenchyl alcohol, (1 mM, c), and norcamphor (1 mM, d) in cells expressing hTRPA1 (n = 14–27). e Changes in fura-2 ratios due to menthol in the presence of test compounds were normalized to changes in the fura-2 ratio by menthol in the absence of test compounds. Data are presented as the mean ± SEM (n = 47–79)