Effects of different doses of intrathecal magnesium on bone cancer pain in mice

Abstract

Objective To investigate the effects of different doses of intrathecal magnesium on bone cancer pain (BCP) in mice.Methods Two hundred and eighty-eight male C3H/HeJ mice,aged 8-10 weeks,weighing 18-22 g,were randomly divided into 6 groups (n =48 each):control group (group C) ; sham operation group (group S) ; BCP + artificial cerebro-spinal fluid (aCSF) 5 μl group (group BCP) ; BCP + MgSO4 14.4 μg group (group M1 ) ; BCP + MgSO4 43.2 μg group (group M2 ) and BCP + MgSO4 86.4 μg group (group M3 ).BCP was produced by injecting fibrosarcoma cells of bone into the medullary cavity of right femur.Intrathecal catheter was placed in the 4 BCP groups.The aCSF 5 μl or MgSO4 14.4μg/5 μl,43.2 μg/5 μl,or 86.4μg/5 μl was injected intrathecally on 14th day after inoculation of tumor cells.The paw withdrawal threshold to mechanical stimuli (PWMT) and paw withdrawal lateney to thermal stimuli (PWTL) were measured at 0.5 h before administration (T0 ) and at 0.5,2,4 and 8 h after administration (T1-4).Eight animals chosen from each group at T0-4 were sacrificed,and L4-5 segment of the spinal cord was removed for determination of NR2B expression (by immuno-flurorescence) in the spinal cord.Results PWMT and PWTL were significantly decreased at T0-4,and NR2B expression was significantly up-regulated at T0-4 in groups BCP,M1,M2,M3 compared with groups C and S ( P ＜0.05).Compared with group BCP,PWMT and PWTL were significandy increased at T1-3,and NR2B expression was significantly down-regulated at T1-3 in groups M2 and M3 ( P ＜ 0.05).Compared with group M2,PWMT and PWTL were significantly increased at T1-3,and NR2B expression was significantly down-regulated at T1-3 in group M3 ( P ＜ 0.05).Conclusion Intrathecal magnesium can reduce BCP in a dose-dependent manner in mice. Key words: Magnesium sulfate; Injections,spinal; Bone neoplasms; Pain