Itch-related responses of dorsal horn neurons to cutaneous allergic stimulation in mice.

This study was conducted to identify the mechanosensitive dorsal horn neurons involved in allergic itch. We examined 98 units responsive to cutaneous allergy; 90 showed only immediate responses, which subsided before the onset of itch-related behavior and eight showed immediate and sustained responses, the latter of which was similar in duration to itch-related behavior, suggesting the involvement of sustained units in itch signaling. Sustained units were localized in the superficial, but not deep, layers of the dorsal horn. They were wide dynamic range or nociceptive specific, but not low threshold and four of eight were noxious heat sensitive. The results suggest that a small minority of neurons in the superficial dorsal horn are involved in allergic itch signals.