Fig. 1.

Itch video paradigm failed to induce contagious itch in mice. a 50 μl saline (or 50 μg / 50 μl histamine) was injected to the observer mice subcutaneously. The mice were put into the transparent home cage with an iPad (white slab, left) or four iPads surrounding the home cage (right) looping the video of demonstrative mice Two cameras (black rectangles) in the corners recorded the behavior of observer mice in 30 min after injection. b Itch-related behavior (Scratching the nape of neck with hind paw, left) and control (right) displayed in the video. c In one iPad paradigm, the video of itch- related behavior did not induce significant increase of scratching behavior mice in observers in which saline was injected (p = 0.737, n = 18 for each group, Student’s t-test). d In four iPads paradigm, the video of itch- related behavior failed to induce significant increase of scratching behavior mice in observers in which saline or lower dose of histamine (50 μg) was injected (F = 0.087, p = 0.769, n = 18 for each saline-injected group, n = 12 for each histamine-injected group, ANOVA). Lower dose of histamine induced enhanced itch in observer mice significantly. *p < 0.05 considered as significant (n = 12 for each group, Student’s t-test)