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

The effects of yokukansan, a traditional Japanese medicine, on aggressiveness and motor activities were examined in mice after injection of amyloid β protein (A β ) 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 A β , 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.