Spontaneous itch in the absence of hyperalgesia in a mouse hindpaw dry skin model

We presently investigated if chronic dry skin treatment of the mouse hindpaw results in itch-related behavior, with or without accompanying hyperalgesia and allodynia. Following a 10-day period of treatment of one hindpaw with a mixture of acetone–diethylether–water (AEW), mice exhibited a significant increase in spontaneous biting behavior directed to the treated hindpaw compared to control animals in which one hindpaw was similarly treated with water only (W). Biting in the AEW group was significantly attenuated by the μ-opioid antagonist naltrexone but was unaffected by the μ-agonist morphine. There were no significant differences in hindpaw heat withdrawal latency, mechanical withdrawal threshold, or cold-plate latency between W and AEW treatment groups. These results indicate that chronic AEW treatment induces spontaneous itch but does not alter pain sensitivity, supporting the utility of this model for studies of chronic dry skin itch.