Inhibitory effect of Byakko-ka-ninjin-to on itch in a mouse model of atopic dermatitis

Byakko-ka-ninjin-to (BN) is composed of gypsum, the root of anemarrhena, gi nseng, licorice and rice. The effect of BN on the inhibition of itch was st udied using an NC mouse model of atopic dermatitis. EN (200 mg/kg, p,o,) si gnificantly inhibited the scratching frequency in NC mice, and decreased th e skin temperature by 1.97 degrees C. The cooling action on the skin by BN may be involved in the inhibitory mechanism of itch, at Least in part, sinc e cooling the skin is known to inhibit the itch sensation in humans. Although the myocyte-specific enhancer binding factor 2C (MEF2C) mRNA is kn own to be increased in the cerebral cortex correlated with the itch sensati on and skin lesions in NC mice, BN did not affect the expression level of t he MEF2C mRNA, This result suggests that the inhibitory effect of BN on itc h does not relate to inhibition of MEF2C expression in the cerebral cortex. The present study indicates that BN has an inhibitory effect on itch, and may be a useful antipruritic drug for atopic dermatitis. Copyright (C) 2000 John Wiley & Sons, Ltd.