OBJECTIVETo explore the analgesic effect of Zhixin Formula (ZF) and its effects on spinal glial fibrillary acidic protein (glial fibillary acidic protein, GFAP, a marker of astrocyte) , CD11b (a maker of microglia), Toll like receptors (TLR2 and TLR4) and nuclear factor κB (NF-κB) in bone cancer pain model rats.

METHODSTotally 20 male SD rats were randomly divided into the blank control group and the bone cancer pain group, 10 in each group. The bone cancer pain model was induced by injecting ascites tumor fluid containing 3 x 10(3) Walker256 cell line from the left tibia. Ethological tests, X-ray test, and HE staining were performed to confirm a successful modeling. After model was successfully established, 70 male SD rats were randomly divided into seven groups, 10 in each group: the blank control group, the bone cancer pain group (as the model group), the Western medicine (WM) group (Tramadol Hydrochloride), the high dose ZF group, the middle dose ZF group, the low dose ZF group, and the Chinese medicine (CM) group (Wulin Zhitong Capsule). Fourteen days after modeling, rats in the high, middle, and low dose ZF groups were administrated by gastrogavage with 9, 4.5, and 2.25 g/kg ZF water condensed preparation respectively, once a day for seven consecutive days. On day 21 MS typical protein expressions including GFAP, CD11b, TLR (2,4) and NF-κB from cornu dorsal medullae spindis L4-L5 were detected by immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and Western blot.

RESULTSCompare with the blank control group, increased weight in the model group was slow and showed a decreasing trend (P < 0.01), spontaneous ambulatory pain score (SAPS) obviously increased (P < 0.01), paw withdrawal threshold (PWT) obviously decreased in the model group (P < 0.05, P < 0.01). Results of lateral tibial X-ray and HE staining showed obvious changes and damage occurred in bone structures of rats in the model group. Immunohistochemistry showed that GFAP expression significantly increased in the model group (P < 0.05). Protein levels of NF-κB also significantly increased in the model group (P < 0.05). Compared with the model group, CD11b expressions obviously decreased in the middle and high dose ZF groups (P < 0.01). Meanwhile, protein expressions of TLR2 and TLR4, as well as NF-κB also obviously decreased (P < 0.05).

CONCLUSIONZF had analgesic effect, which might be probably related to inhibiting proliferation and activation of gliocytes, as well as activation of TLRs and NF-κB.