• Jiajia Dai, Zhuofeng Ding, Jie Zhang, Wei Xu, Qulian Guo, Wangyuan Zou, Yunchuan Xiong, Yingqi Weng, Yong Yang, Sisi Chen, Jun-Ming Zhang, and Zongbin Song.
• From the Department of Anesthesiology, Xiangya Hospital, Central South University, Changsha, Hunan, China.
• Anesth. Analg. 2019 Dec 1; 129 (6): 173317411733-1741.

BackgroundPain and depression are highly prevalent symptoms in cancer patients. They tend to occur simultaneously and affect each other and share biological pathways and neurotransmitters. In this study, we investigated the roles of microglia in the hippocampus in the comorbidity of bone cancer pain and depressive-like behaviors in an animal model of bone cancer pain.MethodsBone cancer pain was induced by injection of Walker 256 mammary gland carcinoma cells into the tibia of rats. The effects of intracerebroventricular administration of microglia inhibitor minocycline were examined.ResultsCarcinoma intratibia injection caused comorbidity of mechanical allodynia and depressive-like behaviors in rats and activation of microglia in the hippocampus. Both mechanical allodynia and depressive-like behaviors were attenuated by minocycline. Enzyme-linked immunosorbent assay analysis showed that the enhanced expressions of M1 microglia marker (CD 86) and the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β in the hippocampus of cancer-bearing rats were decreased by minocycline. On the other hand, minocycline also increased the expressions of M2 microglia marker (MRC1) and anti-inflammatory cytokine interleukin-10.ConclusionsThe results suggest that the activation of microglia in the hippocampus plays an important role in the development of pain and depressive-like behaviors in bone cancer condition.

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