Analgesic Effect Of Intrathecal Fluorocitrate In A Rat Model Of Bone Cancer Pain

Part one Establish a rat model of bone cancer painObjective Using behavioral tests,radiology and histology examination,to establish a rat model of bone cancer pain.Methods A rat model of bone cancer pain was developed by intra-tibial inoculations of Walker-256 carcinoma cells by ascites passaging in Sprague -Dawley rats.Sixteen SD rats were randomly divided into 2 equal groups,Sham group and bone cancer pain group,undergoing injection of Hanks solution and Walker-256 cells into cavitas medullaris of left tibia respectively.Paw withdrawl mechanical threshold(PWMT),thermal withdrawal latencies(TWL)to radiant heat stimulation and ambulatory score were measured at the day before injection and at the 1st,3 rd,7th,1 4th,21th day after injection.The development of the bone tumor and structural damage in the bone were assessed by X-ray scan at the day of 6,12,18 after injection.To examine the extent of bone destruction,the 21th day tumor bearing tibial were sliced to visualize the tumor infiltration and bone destruction by HE stainning.Results 1)In the group of tumor-bearing rats,the mean body weight showed a tendency to decrease during the experiment period(P＜0.01).The rats in Sham group body weight showed an increase(P＜0.05).2)Compared with the sham group,it was found in the bone cancer pain group that PWMT was lowered from the 5th day after operation to the end of the experiment(P＜0.01).ambulatory score was lowered from 14th day after operation(P＜0.05).The radiograph of the tibial showed that slight bone destruction happened on the 6th day and apparent pathological destruction happened on the 18th day.The sections of the bone showed the bone marrow cavity was full of tumor cells,the cortical bone has been destroyed.Conclusion Results from the studies on behavioral tests,radiology and histology suggest that this model of bone cancer has been copied well.Part two:Expression of glia in spinal cord on bone cancer pain ratObjective The role of glia in spinal cord was investigated in the nociceptive information transmitsion by using immunohistochemistry assay.Methods Twenty rats were divided into sham group(n=5),and bone cancer pain group(n=15).In sham group rats were killed on the 7th after Hanks injection,in group bone cancer pain rats were killed on the 7th,14th,21th day after the Walker 256 cells injection,L4～5 ipsilateral lumbar segment of the spinal cord was removed for determination of GFAP and OX-42 expression in the dorsal horn by immunohistochemistry assay.Results 1)Astrocytes activation marker GFAP was deeply stained in ipsilateral spinal cord dorsal horn of group bone cancer pain,the mean optical density was increased from day 7 and increased significantly by day 14 and continuously incerased till day 21(P＜0.01).2) Microglial activation maker OX-42 increased from day 7 and increased significantly by day 14 and continuously incerased till day 21(P＜0.01).Conclusion.Upregulation of spinal glia may be involved in the forming of bone cancer pain.Part three:Analgesic effect of intrathecal fluorocitrate in a rat model of bone cancer painObjective To investigate the effect of intrathecal fluorocitrate on the mechanical hyperalgesia following bone cancer pain(BCP)in rats,and to elucidate the possible role of glia in this model at spinal cord.Methods Female SD rats weighing 150～180g were divided into 2 groups(n=6.each):group PBS,BCP+PBS10μl,group FC,BCP+ fluorocitratel1mol(10μl).On the same day after operation,PE catheter was inserted at the level of lumbar spine and identified by free flow of CSF.On the 14th day afteroperation,PBS or fluorocitrate was administrated,PWMT was measured at 1 h before administration and 1,2,4,6,8,10,12,24h after administration.Results Intrathecal injection fluorocitrate 1nmol can increased the values of PWMT Conclusion Intrathecal injection of Fluorocitrate can upregulate mechanical:pain threshold of bone cancer pain rat.