Effects of yokukansan, a traditional Japanese medicine, on aggressiveness induced by intracerebroventricular injection of amyloid beta protein into mice.

The effects of yokukansan, a traditional Japanese medicine, on aggressiveness and motor activities were examined in mice after injection of amyloid beta protein (Abeta) into the lateral ventricle of the brain. The results were compared with those of conventional (haloperidol) and atypical (risperidone) antipsychotic medicines. A significant increase in aggressiveness was observed on day 7 after injection of Abeta, and it lasted until day 28. A single oral administration of yokukansan (1.0 g/kg) did not ameliorate the aggressiveness observed on day 7. However, a tendency toward amelioration of the aggressiveness was observed after the administration of yokukansan (0.5 and 1.0 g/kg) for 1 week (days 7-14). The 3 week administration (days 7-28) of yokukansan significantly ameliorated the aggressiveness in a dose-dependent manner without inhibition of motor activity. In contrast, a single administration of intraperitoneal haloperidol (0.03-0.1 mg/kg) or oral risperidone (0.1-0.3 mg/kg) on day 28 significantly reduced aggressiveness in a dose-dependent manner. However, motor activities were significantly suppressed. These results suggest yokukansan reduces aggressiveness without suppressing physical activity. Copyright 2009 John Wiley & Sons, Ltd.