Distinct Reactivity of Transient Receptor Potential Vanilloid Subtype 1 in a Murine Model of Atopic Dermatitis with Serious Scratching

Background: Abnormality in skin sensitivity may be responsible for unbearable itch in patients with atopic dermatitis (AD). Objectives: We evaluated reactivity of NC/Tnd mice, a model for human AD, against various experimental stimulations. Methods: Several behavioral tests were performed after external stimuli were applied to NC/Tnd mice. Transient receptor potential vanilloid subtype 1 (TRPV1) reactivity of neuronal cells collected from the dorsal root ganglions (DRG) was analyzed with a Ca++ influx test. Finally, we evaluated suppressive effect of capsaicin on atopic itch of NC/Tnd mice. Results: Pain responses to heat, acidic stimulation, and capsaicin injection, which are transduced through TRPV1, were decreased in NC/Tnd mice, when compared to two standard strains BALB/c and C57BL/6 mice. The reactivity of the primary neurons isolated from DRG to capsaicin was markedly reduced in NC/Tnd mice. Topical application of histamine evoked scratching in NC/Tnd mice as well as other two strains; however, the scratching intensities induced by nonhistamine pruritogens were significantly lower in NC/Tnd mice comparing to the two strains. In conventional NC/Tnd mice with AD, topical application of capsaicin reduced the scratching behavior. Conclusion: TRPV1 is associated with both pain and itch sensation; however, abnormalities in TRPV1 reactivity may involve in severe itch in NC/Tnd mice.