鞘内注射右美托咪定对大鼠吗啡耐受及脊髓炎性反应的影响

Effects of intrathecal administration of dexmedetomidine on morphine tolerance and inflammatory response in rats

目的探讨鞘内注射右美托咪定对大鼠吗啡耐受及脊髓炎性反应的影响。方法采用随机数字表法将33只体质量180~200g雄性SD大鼠,分为3组(n=11):对照组(NS组)、吗啡组(M组)、右美托咪定+吗啡组(Dex组)。NS组鞘内注射无菌生理盐水10μL,1次/d,共7d;M组鞘内注射吗啡15μg,1次/d,共7d;Dex组鞘内注射15μg吗啡和1.5μg右美托咪定,1次/天,共7d。于吗啡鞘内注射第1、3、5、7天给药前和给药后30min测定大鼠的热痛阈。Western blot法检测脊髓中小胶质细胞标记物Iba-1、白细胞介素1β(IL-1β)、肿瘤坏死因子α(TNF-α)和磷酸化p38MAPK(p-p38)的蛋白表达水平。免疫组织化学法检测脊髓Iba-1阳性细胞密度。结果随着吗啡鞘内注射次数增加,M组和Dex组热水甩尾实验最大镇痛效应百分比(MPE)逐渐下降(P<0.05)。与NS组比较,M组甩尾实验MPE在吗啡注射的第1、3、5、7天较高(P<0.05);与M组比较,Dex组甩尾实验MPE于吗啡注射的第3、5、7天较高(P<0.05)。与NS组比较,M组大鼠脊髓Iba-1阳性细胞密度及Iba-1、IL-1β、TNF-α和pp38蛋白表达水平明显升高(P<0.05);与M组比较,Dex组大鼠脊髓Iba-1阳性细胞密度及Iba-1、IL-1β、TNF-α和p-p38蛋白表达水平明显降低(P<0.05)。结论鞘内注射右美托咪定可缓解吗啡耐受的形成,其机制可能与抑制脊髓小胶质细胞介导的炎性反应相关。

Objective To investigate the effects of intrathecal dexmedetomidine administration on the development of morphine tolerance and spinal inflammatory responses. Methods Thirty-three male SD rats weighing 180-200 g were randomly divided into 3 groups （n=11） ：Saline group （group NS）, Morphine group （group M） and Dexmedetomidine group （group Dex）. Animals of group NS were intrathecally injected with 10 μL of saline daily for seven days; Animals in group M were intrathecally injected with 15 μg of morphine daily for seven days; Animals in group Dex were intrathecally injected with a mixture of 15 μg morphine and 1.5μg dexmedetomidine daily for seven days. At 1,3,5 and 7 day of intrathecal injection,hot water tail-flick test were used to evaluate analgesic response to thermal stimuli. After the last episode of behavioral test,Western blot analysis was applied to determine the protein levels of Iba-1 （microglial marker）, IL-1β, TNF-α and phospho-p38MAPK （p-p38） in the spinal cord. In addition, microglia in the spinal cord was immuno-stained with anti-Iba-1 antibody and the densities of microglia were calculated. Results In group M and Dex,the values of maximal possible effect （MPE） in tail-flick test decreased gradually along with repeated morphine administration （P〈0.05）. Compared with group NS,the values of MPE in tail-flick test at 1,3,5 and 7 day of morphine tolerance were higher in group M （P〈0.05）. Compared with group M,the values of MPE in tail-flick test at 3,5 and 7 day of morphine tolerance were higher in group Dex （P〈0.05）. Compared with group NS,the spinal protein levels of Iba-1 ,IL-1β,TNF-α and p-p38 as well as the density of Iba-1 positive cells in group M were increased （P〈0.05）. However,Compared with group M,the of Iba-1 ,IL-1β, TNF-α and p-p38 as well as the density of Iba-1 positive cells were decreased（P〈0, 05）. Conclusion Intrathecal dexmedetomidine administration can attenuate morphine tolerance by inhibiting microglia-mediated inflammatory responses in the spinal cord.