Model Of Bone Cancer Pain And Its Spinal Cord Expression Of Gfap Level Changes

ObjectiveThe aim of this investigation was to set up tibial cancer pain model with Walker 256 mammary gland carcinoma cells in rats,and compare differences of painful behaviors with inflammatory & neuropathic pain model.GFAP that has been implicated in the generation and maintenance of chronic pain was then examined in spinal cord by IHC method and evaluated whether its expression was different in three chronic pain models.Methods36 female SD rats were randomly divided into 4 groups:â‘ Sarcoma(n=8,tumor cells were injected);â‘¡Sham1(n=10,rat ascetic fluid without tumor cells was injected);â‘¢Sham 2(n=10,NS was injected);â‘£Na(i|¨)ve(n=8).According to the method described by Medhurst et al,10⁵ syngenenic Walker 256 mammary gland carcinoma cells,ascetic fluid without tumor cells and NS were respectively injected into the tibia medullary cavity via intercondylar eminence.Series of tests were carried out including general condition,weight bearing ability,ambulatory pain,MWT,PWTL together with bone radiology and bone histology.Another 52 female SD rats were randomly divided into 6 groups:â‘ CFA(n=10);â‘¡NS(n=8);â‘¢PNL(n=9);â‘£Sham(n=9);⑤⑥Na(i|¨)ve(n=8), and underwent as above.All rats were sacrificed at the period of remarkable pain.GFAP was then examined in spinal cord by IHC method and evaluated whether its expression was different in three chronic pain models.ResultsRats that developed of hyperalgesia and allodynia after intra-tibial injection of Walker 256 cells were proved successful.MWT and PWTL were measured during the experimental days,and the findings revealed Sarcoma rats started to exhibit mechanical allodynia on the 7^th day and thermal hyperalgesia on the 11^th day after the operation(P＜0.01).At the period of remarkable pain,CFA rats exhibited mechanical allodynia stronger than Sarcoma and PNL rats(P＜0.01),but no difference was observed between Sarcoma and PNL rats(P＞0.05).The difference of thermal hyperalgesia between three chronic pain models was not remarkable(P＞0.05).The up-regulation of GFAP expression in spinal cord of Sarcoma rats was significantly greater than that induced by PNL(P＜0.05) and CFA(P＜0.01) model.The up-regulation of GFAP in PNL model was significantly greater than that induced by CFA model(P＜0.01).Compared to Sham or Na(i|¨)ve group, no change of GFAP was observed in the spinal cord of CFA.The data suggests that the mechanisms of bone cancer pain are complicated and different from inflammatory and neuropathic pain.