Rikkunshito, a japanese kampo medicine, ameliorates decreased feeding behavior via ghrelin and serotonin 2b receptor signaling in a Novelty Stress Murine Model

Abstract

We investigated the effects of rikkunshito (RKT), a ghrelin signal enhancer, on the decrease in food intake after exposure to novelty stress in mice. RKT administration (500 mg/kg, per os) improved the decrease in 6 h cumulative food intake. In control mice, the plasma acylated ghrelin levels significantly increased by 24 h fasting. In contrast, the acylated ghrelin levels did not increase by fasting in mice exposed to the novelty stress. RKT administration to the novelty stress mice showed a significant increase in the acylated ghrelin levels compared with that in the distilled-water-treated control mice. Food intake after administering serotonin 2B (5-HT receptor antagonists was evaluated to clarify the role of 5-HTreceptor activation in the decrease in feeding behavior after novelty stress. SB215505 and SB204741, 5-HTreceptor antagonists, significantly improved the decrease in food intake after exposure to novelty stress. A component of RKT, isoliquiritigenin, prevented the decrease in 6 h cumulative food intake. Isoliquiritigenin showed 5-HTreceptor antagonistic activity in vitro. In conclusion, the results suggested that RKT improves the decrease in food intake after novelty stress probably via 5-HTreceptor antagonism of isoliquiritigenin contained in RKT. © 2013 Chihiro Yamada et al.