c-fos expression in superficial dorsal horn of cervical spinal cord associated with spontaneous scratching in rats with dry skin

Using a dry skin model in rats, we assessed spontaneous itch-related scratching behavior and associated c-fos expression in the superficial dorsal horn of the spinal cord. The number of spontaneous bouts of hind limb scratching directed toward the nape of the neck was significantly higher after 5 days of topical application of acetone-diethylether-water (AEW) compared to pre-treatment levels or to control animals treated with water only. In AEW-treated animals, neurons expressing Fos-like immunoreactivity (FLI) were observed in superficial laminae of the dorsal horn at C3-C5 levels. There was a significant, positive correlation between the number of neurons in lamina I expressing FLI and the number and cumulative duration of spontaneous scratching bouts. These results suggest that this model may be useful to assess mechanisms of dry skin pruritus, and that lamina I neurons are activated as a consequence of itching and/or scratching in this model.