Variation of spinal microglia in a SD rat model of bone cancer pain

Objective To explore the spinal microglial alteration in a rat model of bone cancer pain produced by injecting syngeneic Walker 256 rat mammary gland cancer cells into the unilateral tibia of female SD rats. Methods Bone cancer pain model was created by receiving left superior extremity intra-tibial inoculations of Walker 256 syngeneic SD rat carcinoma cells which were cultured and proliferated in vivo to produce ascites in 25 female SD rats weighing 150-180 g. The rats were divided by 5 groups randomly:significantly enhanced and activated in the L4-L6 superficial spinal cord bilateralis in rats with inoculatin of Walker cancer cells, characterized by enhanced immunostaining of OX-42 (microglial marker,P< 0.05,P <0.01). Spinal OX-42 staining progression was decreased on the day 6 to day 18 post cell inoculation,and it was distinguished on the day 6 post inoculation (P <0.05 ,P <0.01). Conclusion The injection of Walker 256 cancer cells into the tibia activates the spinal microglia. Furthermore, the microglia activated in ipsi-and contralateral superficial dorsal horns highlights the possible involvement in the mirror imaging pain phenomenon in neuroethology of this model of bone cancer pain. Microglia may play important role in the emerge of bone cancer pain in the earlier phase. Key words: Bone cancer pain; Microglia; Spinal cord