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Effects of intrathecal administration of AM22-52 on mechanical allodynia and CCL2 expression in DRG in bone cancer rats

CHEN Ya-Juan, HUO Yuan-Hui, HONG Yanguo^*

College of Life Sciences, Fujian Normal University, Fujian Key Laboratory of Developmental Biology and Neuroscience, Fuzhou 350117, China

Abstract

The pain peptide adrenomedullin (AM) plays a pivotal role in pathological pain. The present study was designed to investigate the effect of blockade of AM receptor on bone cancer pain (BCP) and its mechanism. BCP was developed by inoculation of Walker 256 mammary gland carcinoma cells in the tibia medullary cavity of Sprague Dawley rats. The selective AM receptor antagonist AM22-52 was administered intrathecally on 15 d after the inoculation. Quantitative real-time PCR was used to detect mRNA level of CC chemokine ligand 2 (CCL2) in dorsal root ganglion (DRG). Double immunofluorescence staining was used to analyze the localizations of CCL2 and AM in DRG of normal rats. The results showed that, from 6 to15 d after the inoculation, the animals showed significant reduction in the mechanical pain threshold in the ipsilateral hindpaw, companied by the decline in bone density of tibia bone. The expression of CCL2 mRNA in DRG of BCP rats was increased by 3 folds (P < 0.001 vs saline group). Intrathecal administration of AM22-52 abolished bone cancer-induced mechanical allodynia and increase of CCL2 mRNA level (P < 0.001). In normal rats, CCL2 was co-localized with AM in DRG neurons. These results suggest that AM may play a role in the pathogenesis of BCP. The increased AM bioactivity up-regulates CCL2 expression in DRG, which may contribute to the induction of pain hypersensitivity in bone cancer.

Key words: Adrenomedullin; CC chemokine ligand 2 ; bone cancer pain ; dorsal root ganglion

Received: 2016-06-14　　Accepted: 2016-09-14

Corresponding author: 洪炎国　　E-mail: yhong@fjnu.edu.cn

Citing This Article：

CHEN Ya-Juan, HUO Yuan-Hui, HONG Yanguo. Effects of intrathecal administration of AM22-52 on mechanical allodynia and CCL2 expression in DRG in bone cancer rats. Acta Physiol Sin 2017; 69 (1): 70-76 (in Chinese with English abstract).