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

摘要

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180～200 g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7 d;M组鞘内注射吗啡15 μg,1次/d,共7 d;Dex组鞘内注射15 μg吗啡和1.5 μg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30 min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p-p38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 tμL 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 15μg morphine and 1.5 μg 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-a 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-1L 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.