A single dose of interleukin‐31 (IL‐31) causes continuous itch‐associated scratching behaviour in mice

Abstract We investigated the effects of a single dose of mouse interleukin‐31 ( IL ‐31) on scratching behaviour in comparison with spontaneous skin‐lesion‐ or serotonin (5‐ HT )‐ induced scratching behaviour in NC /Nga and BALB /c mice. Intradermal (i.d.) injection of IL ‐31 caused a gradual increase in long‐lasting scratching ( LLS , over 1.5 s) about 3 h after administration followed by a gradual decrease for over 24 h after administration. I.d. injection of IL ‐31 significantly increased the total LLS counts/24 h but not short‐lasting scratching ( SLS , 0.3–1.5 s). In skin‐lesioned NC /Nga mice, the LLS but not SLS counts were significantly higher than those in non‐skin‐lesioned NC/Nga mice. We also investigated 5‐ HT ‐induced scratching in BALB /c mice, SLS but not LLS increased immediately after the injection and then decreased to baseline after at 20 min. These results suggest that IL ‐31 may participate in the sensation of itching and promote scratching behaviour in skin‐lesioned NC /Nga mice, an animal model of atopic dermatitis ( AD ).