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Behavioral evidence for the differential regulation of p-p38 MAPK and p-NF-κB in rats with trigeminal neuropathic pain

Min K Lee1, Seung R Han1, Min K Park1, Min J Kim1, Yong C Bae2, Sung K Kim3, Jae S Park4 and Dong K Ahn1*

  • * Corresponding author: Dong K Ahn dkahn@knu.ac.kr

  • † Equal contributors

Author Affiliations

1 Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu, Korea

2 Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, Korea

3 Department of Endodontics, School of Dentistry, Kyungpook National University, Daegu, Korea

4 Department of Physiology, School of Medicine, Kyungpook National University, Daegu, Korea

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Molecular Pain 2011, 7:57  doi:10.1186/1744-8069-7-57

Published: 5 August 2011

Abstract

Background

We investigated the differential regulation of p-p38 MAPK or p-NF-κB in male Sprague-Dawley rats with inferior alveolar nerve injury resulting from mal-positioned dental implants. For this purpose, we characterized the temporal expression of p-p38 MAPK or p-NF-κB in the medullary dorsal horn and examined changes in nociceptive behavior after a blockade of p-p38 MAPK or p-NF-κB pathways in rats with trigeminal neuropathic pain.

Results

Under anesthesia, the left lower second molar was extracted and replaced with a mini dental implant to intentionally injure the inferior alveolar nerve. Western and immunofluorescence analysis revealed that p-p38 MAPK is upregulated in microglia following nerve injury and that this expression peaked on postoperative day (POD) 3 through 7. However, the activation of p-NF-κB in astrocyte peaked on POD 7 through 21. The intracisternal administration of SB203580 (1 or 10 μg), a p38 MAPK inhibitor, on POD 3 but not on POD 21 markedly inhibits mechanical allodynia and the p-p38 MAPK expression. However, the intracisternal administration of SN50 (0.2 or 2 ng), an NF-κB inhibitor, on POD 21 but not on POD 3 attenuates mechanical allodynia and p-NF-κB expression. Dexamethasone (25 mg/kg) decreases not only the activation of p38 MAPK but also that of NF-κB on POD 7.

Conclusions

These results suggest that early expression of p-p38 MAPK in the microglia and late induction of p-NF-κB in astrocyte play an important role in trigeminal neuropathic pain and that a blockade of p-p38 MAPK at an early stage and p-NF-κB at a late stage might be a potential therapeutic strategy for treatment of trigeminal neuropathic pain.