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BioMed Research International
Volume 2013 (2013), Article ID 792940, 9 pages
http://dx.doi.org/10.1155/2013/792940
Research Article

Rikkunshito, a Japanese Kampo Medicine, Ameliorates Decreased Feeding Behavior via Ghrelin and Serotonin 2B Receptor Signaling in a Novelty Stress Murine Model

1Tsumura Research Laboratories, Tsumura & Co., Ibaraki 300-1192, Japan
2Pathophysiology and Therapeutics, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Hokkaido 060-0812, Japan
3Department of Gastroenterology and Hepatology, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido 060-8638, Japan
4Department of Medical Gastroenterology, National Hospital Organization Hokkaido Medical Center, Sapporo, Hokkaido 063-0005, Japan

Received 28 June 2013; Revised 21 August 2013; Accepted 29 August 2013

Academic Editor: Mahmood Ameen Abdulla

Copyright © 2013 Chihiro Yamada et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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-HT2B) receptor antagonists was evaluated to clarify the role of 5-HT2B receptor activation in the decrease in feeding behavior after novelty stress. SB215505 and SB204741, 5-HT2B receptor 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-HT2B receptor antagonistic activity in vitro. In conclusion, the results suggested that RKT improves the decrease in food intake after novelty stress probably via 5-HT2B receptor antagonism of isoliquiritigenin contained in RKT.