Figure 1.

Cheek model of dry skin pruritus induces scratching and epidermal thickening. A, Time course for the dry skin assay in the mouse cheek. First day: the right cheek of each mouse was shaved. Days one to five: the shaved cheek was treated twice daily with a 1:1 mixture of acetone and ether, followed by water. Scratching behaviors were recorded for 20 min on days three and five after the second AEW treatment. Mouse cheeks were removed for histological analysis following recording on either day three or day five. B, Photo displaying the area of treatment in the cheek model of itch C, Scratching behaviors were observed on day three and day five of cheek treatment. The total time spent scratching was quantified for 20 min. Application of vehicle (VEH, water) failed to elicit scratching or wiping. All error bars represent SEM (n ≥ 12 mice/group, **p < 0.01, one-way ANOVA). D, H&E-stained cheek skin sections from mice treated for 3 d (top) or 5 d (bottom) with AEW on ipislateral (right) and VEH on contralateral cheeks (left). E indicates epidermis; D, dermis. E, Thickness of nucleated epidermal layers was quantified from AEW-treated and VEH-treated skin. Means ± SEM are shown (n = 16 –24 sections from two mice per group, ***p < 0.002, Student’s two-tail t test).