TRPA1 protein and mRNA expression in the trachea and skin tissues of guinea pigs, as detected by western blot and RT-PCR, respectively. (A) Cold exposure increased expression of the TRPA1 protein in the trachea of guinea pigs with cough (model), but not in healthy guinea pigs (control). Similar enhancement of TRPA1 overexpression was observed in the guinea pigs with cough, following exposure of the whole body (model, whole-body exposure) and trunk-limbs (model, trunk-limb exposure), but not the head (model, head exposure), to a cold environment. (B) Cold exposure increased the expression of TRPA1 protein in the skin of healthy guinea pigs (control, whole-body exposure), and guinea pigs with cough (model), following exposure of the whole body (model, whole-body exposure) and trunk-limbs (model, trunk-limb exposure), but not the head (model, head exposure), to a cold environment. (C) TRPA1 mRNA expression in the trachea was similar to TRPA1 protein expression among the different groups of guinea pigs, as presented in panel (A). (D) The increase in TRPA1 mRNA expression in the skin was remarkable only in the guinea pigs with cough, following exposure of the whole body (model, whole-body exposure) and trunk-limbs (model, trunk-limb exposure) to a cold environment. Results are presented as the mean ± SD (n = 5; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001).