Biol Pharm Bull. 2003 Jun; 26(6): 896-8.

Inhibitory effect of the repeated treatment with Unsei-in on substance P-induced itch-associated responses through the downregulation of the expression of NK(1) tachykinin receptor in mice.

Andoh T, Honma Y, Kawaharada S, Al-Akeel A, Nojima H, Kuraishi Y.

Department of Applied Pharmacology, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan.

Unsei-in, a traditional medicine, is prescribed against pruritic cutaneous diseases, but the mechanisms of antipruritic action are still unknown. In the present study, we examined the antipruritic effects of Unsei-in in mice. Single administration of Unsei-in did not inhibit substance P-induced itch-associated response (scratching) in mice. However, repeated treatment with Unsei-in for 7 d significantly inhibited substance P-induced scratching. The same repeated treatment with Unsei-in suppressed the expression of NK(1) tachykinin receptors in the skin. These results suggest that Unsei-in inhibits substance P-associated itching and that the inhibition is at least partly due to the suppression of the expression of NK(1) tachykinin receptors in the skin.