Figure 4.

TRPA1 is required for dry-skin-evoked itch behaviors and morphological changes in the skin. A, Dry-skin-evoked scratching was measured in wild-type (WT AEW; black), TRPV1^−/− (V1 AEW; gray), and TRPA1^−/− (A1 AEW; red) mice after 3 and 5 d of AEW treatment to the cheek. The total time spent scratching was quantified for 20 min. Treatment with vehicle on wild-type mice (VEH, water) failed to elicit scratching or wiping (VEH; white). All error bars represent SEM (n ≥ mice/genotype, **p < 0.01). B, Dry-skin-evoked scratching was measured in wild-type mice on AEW treatment on days three and five immediately after (≤ 2 min) subcutaneous injection with control PBS (CON) or the TRPA1 inhibitor HC-030031 (HC). The total time spent scratching was quantified for 20 min postinjection and normalized to CON-treated mice. All error bars represent SEM (n ≥ 9 mice/genotype or treatment, **p < 0.01). C, H&E-stained skin sections from wild-type mice (WT; top) and TRPA1^−/− littermates (A1^−/−; bottom) treated ipsilaterally with AEW (left) and contralaterally with VEH. E indicates epidermis; D, dermis. D, The increase in epidermal thickness induced by AEW was quantified from four to five mice per condition. NS indicates the “no scratching” condition in the caudal back model. Means ± SEM are shown (*p = 0.01, Student’s two-tail t test).