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Original Article

Korean J Pain 2012; 25(1): 1-6

Published online January 31, 2012 https://doi.org/10.3344/kjp.2012.25.1.1

Copyright © The Korean Pain Society.

Analgesic Effects of Intrathecal Curcumin in the Rat Formalin Test

Yong Ku Han, MD, Seong Heon Lee, MD, Hye Jin Jeong, MD, Min Sun Kim, MD, Myung Ha Yoon, MD, and Woong Mo Kim, MD*

Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.

Correspondence to: Woong Mo Kim, MD. Department of Anesthesiology and Pain Medicine, Chonnam National University Medical School, 671, Jebong-ro, Dong-gu, Gwangju 501-757, Korea. Tel: +82-62-220-6893, Fax: +82-62-232-6294, kimwm@chonnam.ac.kr

Received: November 14, 2011; Revised: November 30, 2011; Accepted: December 5, 2011

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Curcumin has been reported to have anti-inflammatory, antioxidant, antiviral, antifungal, antitumor, and antinociceptive activity when administered systemically. We investigated the analgesic efficacy of intrathecal curcumin in a rat model of inflammatory pain.

Methods

Male Sprague Dawley rats were prepared for intrathecal catheterization. Pain was evoked by injection of formalin solution (5%, 50 µl) into the hind paw. Curcumin doses of 62.5, 125, 250, and 500 µg were delivered through an intrathecal catheter to examine the flinching responses. The ED50 values (half-maximal effective dose) with 95% confidence intervals of curcumin for both phases of the formalin test were calculated from the dose-response lines fitted by least-squares linear regression on a log scale.

Results

In rats with intrathecal administration of curcumin, the flinching responses were significantly decreased in both phases. The slope of the regression line was significantly different from zero only in phase 2, and the ED50 value (95% confidence interval) of curcumin was 511.4 µg (23.5-1126.5). There was no apparent abnormal behavior following the administration of curcumin.

Conclusions

Intrathecal administration of curcumin decreased inflammatory pain in rats, and further investigation to elucidate the precise mechanism of spinal action of curcumin is warranted.

Keywords: antinociception, curcumin, formalin test, spinal cord