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Evidence-Based Complementary and Alternative Medicine
Volume 2012, Article ID 953459, 8 pages
Research Article

Antiallodynic Effect of Herbal Medicine Yokukansan on Peripheral Neuropathy in Rats with Chronic Constriction Injury

1Tsumura Research Laboratory, Tsumura & Co., 3586 Yoshiwara, Ami-machi, Inashiki-gun, Ibaraki 300-1192, Japan
2Department of Anesthesiology and Pain Medicine, Juntendo Tokyo Koto Geriatric Medical Center, 3-3-20 Shinsuna, Koto-ku, Tokyo 136-0075, Japan

Received 16 June 2011; Accepted 2 November 2011

Academic Editor: Alvin J. Beitz

Copyright © 2012 Yasuyuki Suzuki 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.


Yokukansan, one of the traditional Japanese herbal medicines, ameliorated neuropathic pain symptoms in patients. In this study, we investigated the effects of yokukansan on neuropathic pain in chronic constriction injury (CCI) model. Oral administration of yokukansan significantly inhibited mechanical and cold allodynia in the von Frey hair or acetone test, respectively. In comparison, amitriptyline, a tricyclic antidepressant, demonstrated moderate, but not significant, antiallodynic effects in the mechanical and cold tests. Yokukansan significantly inhibited the cerebrospinal fluid dialysate level of glutamate that had increased by the stimulation of brush or acetone. Glutamate transporter inhibitors, DL-threo-beta-hydroxy aspartate and dihydrokainate, decreased the yokukansan-induced antiallodynic actions in CCI rats. Our results suggest that yokukansan was confirmed to have antiallodynic effects in CCI rats, which are related to a blockade of glutamatergic neurotransmission via activation of glutamate transporters in the spinal cord.