Objective: To study the analgesic effect and central mechanism of CQ compound in rat models with tibia metastatic cancer pain. Method: Female Wistar rats were randomly divided into sham operation group and surgery group

with operation control and tibia metastatic cancer pain operation for Walker-256 breast cancer cells respectively. The 40 successfully modeled rats were randomly divided into model group

CQ high dose (CQ-H) group (200 mg · kg-1)

CQ middle dose (CQ-M) group (150 mg · kg-1)

CQ low dose (CQ-L) group (100 mg · kg-1) and gabapentin group (100 mg · kg-1)

8 rats in every group. Mechanical withdrawal threshold (MWT) measured by von frey hairs fiber filament was used to evaluate rats' pain behavior. Microdialysis was used to detect glutamate (Glu) level of cerebrospinal fluid; radioimmunoassay was used to detect substance P (SP) and β-endorphin (β-EP) contents in L4-L6 spinal cord sections; and Aim Plex Multiple Immunoassay was used to detect the

interleukin-12 (IL-12-P70) and β-nerve growth factor (β-NGF) levels of tumor local tissues. Result: As compared with the model group

CQ compound groups and gabapentin group significantly increased MWT of rats; MWT of rats in CQ compound groups began to rise in 30 min after administration

and peaked in 60 min (P<0.05

P<0.01). Threshold elevation in CQ-H

CQ-M

and CQ-L groups showed dose effect relationship

and the analgesic effect of three consecutive days administration was stronger than that of single dose administration; CQ compound and gabapentin reduced the level of glutamate

SP and β-EP (P<0.05)

and raise the level of IL-12-P70 (P<0.05). Conclusion: CQ compound can relieve the bone cancer pain of rat models

and its effect intensity is similar to that of gabapentin. Its analgesic mechanism may be associated with suppressing the central excitatory amino acids

pain-associated neuromodulator and peripheral nerve growth factor and promoting IL-12-P70 in immunological reaction.