Inhibitory effects of methanol extracts of herbal medicines on substance P-induced itch-scratch response

In a search for new anti-pruritic drugs we screened methanol extracts of 33 herbal medicines which have been used for cutaneous diseases for their ant ipruritic activity using substance P (SP) as a pruritogen in mice. When adm inistered perorally 30 min before SP injection, methanol extracts of 6 of t hese herbal medicines, the root of Scrophularia ningpoensis HEMSL., the roo t of Patrinia villosa (THUNB.) JUSS, the fruit of Forsythia suspenna VAHL, the rhizome of Cimicifuga dahurica (TURCZ.) MAXIM., the aerial part of Schi zonepeta tenuifolia BRIQ. and the fruit of Cnidium monnieri (L.) CUSS, inhi bited SP-induced itch-scratch response at a dose of 200 mg/kg without affec ting locomotor activity. Dose dependence of these 6 extracts (50-500 mg/kg) was investigated and all of them inhibited SP-induced itch-scratch respons e, with extracts from Scrophularia ningpoensis, Schizonepeta tenuifolia and Cnidium monnieri showing particularly significant inhibition. The results suggest that these 6 methanol extracts have inhibitory activity against SP- induced itching.