Articles

Article

Original

Exp Neurobiol 2005; 14(2): 67-77

Published online December 31, 2005

© The Korean Society for Brain and Neural Sciences

Role of Cyclooxygenases Isoforms in the Dorsal Root Ganglia during Inflammatory Pain Transmission

Jee-In Chung1,2†, Yun Young Lee1†, Eun Joo Kim1, You-Na Jang1,2, Yi-Sook Jung1, Soo Hwan Lee1, Chang-Hyun Moon1, Seung Hwa Park3 and Eun Joo Baik1,2*

1Department of Physiology, 2Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon 442-749, 3Department of Anatomy, College of Medicine, Kon-Kuk University, Chungju 380-701, Korea

Correspondence to: *To whom correspondence should be addressed.
Equal contributor.
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e-mail: eunjoo@ajou.ac.kr

Abstract

Prostaglandins (PGs) and their rate-limiting enzymes, cyclooxygenase (COX) isoforms (COX-1 and COX-2), have important roles in transmission of noxious information. In the present experiment, we examined the differential analgesic and anti-inflammatory effects of COX isoform inhibitors, and the distribution of COX isoforms within the dorsal root ganglia. COX-2 inhibitor, rather than COX-1 preferential inhibitor such as aspirin significantly attenuated Freund's complete adjuvant (FCA)-induced edema; however, nimesulide, a selective COX-2 inhibitor, did not alleviate FCA-induced mechanical hyperalgesia, even as aspirin, a preferential COX-1 inhibitor reduced the hyperalgesia. In normal DRG, COX-1 was abundant in neurons, satellite cells and Schwann cells. COX-2 was rare in neurons, while very strong in satellite cells and in the lining of blood vessels. In the DRG of the inflammatory state, COX-1 and COX-2 protein slightly increased after FCA injection, especially in the neuron. However, COX-2 mRNA was little detected in normal and inflammatory state, whereas COX-1 mRNA in the ipsilateral DRG increased 6 days after FCA, and COX-1 mRNA in the ipsilateral DRG in situ was greatly expressed, especially in satellite cells or neurons. The changes of PGI2 and PGE2, rather than PGF in DRG correspond well with the pain behavior. In conclusion, COX-1 rather than COX-2 in the DRG might play a potential role in nociceptive transmission of peripheral inflammation.

Keywords: inflammation, pain, cyclooxygenase isoforms, dorsal root ganglia