Abstract
The antihistaminic action of eighteen herbal medicines was investigated by the radioligand binding and functional assays. The hexane fractions of Trichosanthis radix, Mori cortex radicis and Evodiae fructus dosedependently inhibited [$^3$H] mepyramine binding to H$_1$, receptor in guinea-pig brain homogenates and histamine-induced contraction of isolated guinea-pig ileum. Antihistaminic action of the hexane and ethyl acetate fractions of Mori cortex radicis and the hexane fraction of Evodiae fructus was more potent than their antimuscarinic action evaluated from the inhibition of [$^3$H]QNB binding and carbachol response. The ethyl acetate and chloroform fractions from Scutellariae radix also inhibited histamine-induced contraction, but antihistaminic potencies of these fractions were almost identical with their antimuscarinic potencies. The hexane fractions of Mori cortex radicis and Evodiae fructus inhibited selectively the increase of histamine-induced cutaneous vascular Permeability in the rat dorsal skins. However, the ethyl acetate fraction from Scutellariae radix inhibited eqipotently the effects of histamine and serotonin on the vascular permeability. These results demonstrate that the hexane and ethyl acetate fractions of Mori cortex radicis and the hexane fraction of Evodiae fructus have the selective histamine H$_1$receptor blocking activity.
