48 Circadian Regulation of Scratching Behavior in NC/TND Mice, a Mouse Model for Human Atopic Dermatitis

BACKGROUND: Scratching behavior is a pivotal clinical sign and a therapeutic target of atopic dermatitis; however, due to the lack of an appropriate animal model, circadian regulation of this behavior remains unclear. METHODS: NC/Tnd mice, a mouse model for human atopic dermatitis, have been shown to exhibit severe scratching behavior together with the development of spontaneous atopic dermatitis when they are raised under air-uncontrolled environment. In this study, scratching behavior of the mice was measured by a SCLABA-Real system, a newly developed equipment that provides us with the real-time, long-term, quick and accurate quantification of murine scratching behavior by analyzing images with the high-speed camera and the invisible near-infrared light. RESULTS: Analysis by a SCLABA-Real system demonstrated that the frequency and duration of scratching behavior significantly correlated with the exacerbation of dermatitis in the mice, indicating that this system was able to measure scratching behavior without putting stress upon the mice. Twenty-four hours analysis revealed that the frequency and duration of scratching behavior increased in from the afternoon to the midnight and decreased in the morning. In addition to scratching behavior, transepidermal water loss (TEWL) also changed during a day in the mice. TEWL increased in the midnight and decreased in the morning. CONCLUSIONS: These results indicate that scratching behavior and skin barrier function in atopic dermatitis exhibited circadian rhythm. In addition, NC/Tnd mice are considered to be an appropriate mouse model to investigate circadian rhythm of scratching behavior associated with atopic dermatitis.