Memory and learning-enhancing effect of Daikenchuto, a traditional Japanese herbal medicine, in mice

The effect of Daikenchuto (DKT), a traditional Japanese herbal medicine (Kampo medicine), and its constituents (ginger rhizome, ginseng root, rice gluten and Zanthoxylum fruit) on the memory formation process was examined in mice by means of a Morris water maze test. The administration of DKT [300-4000 mg/kg, administered orally (p.o.)] for 3 consecutive days dose-dependently shortened the time required by the mice to find the platform in the water maze test relative to the control. Among the four constituents of DKT, the extract of Zanthoxylum fruit (70 mg/kg, the dose equivalent to 4000 mg/kg DKT) administered p.o. for 3 consecutive days significantly promoted the memory and learning rate. The memory- and learning-enhancing effect was potently elicited by 5 mg/kg (p.o., 2 days) hydroxy-sanshool, the active component of the ethyl acetate fraction of Zanthoxylum fruit. In another series of experiments with the water maze test, the administration of scopolamine [1 mg/kg, intraperitoneally (i.p.)] for 3 consecutive days significantly prolonged the time needed by the mice to find the platform. The subsequent administration of DKT (4000 mg/kg, p.o.) for 3 consecutive days possessed an abatement effect on the scopolamine-induced dementia. The present results indicate that DKT and, more specifically, its constituent Zanthoxylum fruit and the active component of Zanthoxylum fruit, hydroxy-sanshool, all have a memory- and learning-enhancing effect and are probably associated with the release of acetylcholine from neuronal terminals in the brain.