BACKGROUND: The aim of this study was to investigate the role of chemokine (C-X-C motif) ligand 13 (CXCL13) in morphine tolerance in rats with cancer-induced bone pain (CIBP).

MATERIAL AND METHODS: We established a rat CIBP model and a rat CIBP-morphine tolerance (BM) model. BM rats were intrathecally administered rmCXCL13, neutralizing anti-CXCL13, and normal saline, while the control group rats underwent a sham operation and were injected with normal saline. The morphine analgesia was assessed by measuring mechanical withdrawal threshold (MWT) and mechanical withdrawal duration (MWD) at various time points. The co-expressions of CXCL13 and NeuN were measured by immunofluorescence double-staining. CXCL13 protein and mRNA expressions were detected by Western blot and quantitative real-time polymerase chain reaction (RT-qPCR), respectively.

RESULTS: Compared to the sham-operation (S) group, the BM group showed obviously decreased MWT and increased MWD on Day 9 after CIBP, but obviously increased MWT and decreased MWD on Day 3 after morphine administration; subsequently, the MWT was decreased and MWD was increased (all P<0.05). In comparison with the S+saline group, increased MWT and decreased MWD were observed in BM rats on Day 3 after anti-CXCL13 administration, and obviously decreased MWT and increased MWD were found in BM rats on Day 3 after rmCXCL13 administration (all P<0.05).

CONCLUSIONS: Up-regulated CXCL13 has a negative role in morphine analgesia in relief of CIBP, which may provide a new target for the management of CIBP.

Keywords: Analgesia - methods, Antibodies, Neutralizing - pharmacology, Bone Neoplasms - physiopathology, Cancer Pain - physiopathology, Chemokine CXCL13 - immunology, Drug Tolerance, Mammary Neoplasms, Experimental - physiopathology, Morphine - pharmacology, Pain Management - methods, RNA, Messenger - genetics, Random Allocation, Spinal Cord - metabolism, Up-Regulation - drug effects