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Open Access Research

Ethyl pyruvate attenuates formalin-induced inflammatory nociception by inhibiting neuronal ERK phosphorylation

Min Jung Lee12, Minhee Jang1, Hyuk-Sang Jung1, Sung-Hoon Kim2 and Ik-Hyun Cho1*

Author Affiliations

1 Department of Anatomy, College of Oriental Medicine, and Institute of Oriental Medicine, Kyung Hee University, Seoul, 130-701, Republic of Korea

2 Cancer Preventive Material, Development Research Center, College of Oriental Medicine, Kyung Hee University, Seoul, 130-701, Republic of Korea

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Molecular Pain 2012, 8:40  doi:10.1186/1744-8069-8-40

Published: 28 May 2012

Abstract

Background

Ethyl pyruvate (EP) possesses anti-inflammatory activity. However, the potential anti-nociceptive value of EP for the treatment of the inflammatory nociception is largely unknown. We investigated whether EP could have any anti-nociceptive effect on inflammatory pain, after systemic administration of EP (10, 50, and 100 mg/kg, i.p.), 1 hour before formalin (5%, 50 μl) injection into the plantar surface of the hind paws of rats.

Results

EP significantly decreased formalin-induced nociceptive behavior during phase II, the magnitude of paw edema, and the activation of c-Fos in L4-L5 spinal dorsal horn. EP also attenuated the phosphorylation of extracellular signal-regulated kinase (ERK) in the neurons of L4-L5 spinal dorsal horn after formalin injection. Interestingly, the i.t. administration of PD98059, an ERK upstream kinase (MEK) inhibitor, completely blocked the formalin-induced inflammatory nociceptive responses.

Conclusions

These results demonstrate that EP may effectively inhibit formalin-induced inflammatory nociception via the inhibition of neuronal ERK phosphorylation in the spinal dorsal horn, indicating its therapeutic potential in suppressing acute inflammatory pain.

Keywords:
Ethyl pyruvate; Inflammatory nociception; c-Fos; Phospho-ERK; PD-98059