Effect of intrathecal injection of dexmedetomidine on protein kinase C expression of spinal dorsal horn neurons in a rat model of chronic neuralgia

doi:10.3969/j.issn.2095-4344.2014.29.016

Abstract

Abstract:

BACKGROUND: Dexmedetomidine is an efficient, highly selective alpha-2 adrenergic receptor agonist, with sedative, analgesia and anti-anxiety effects, it has little impact on the respiration.

OBJECTIVE: To observe the analgesic effect induced by intrathecal injection of dexmedetomidine in rat model of spared nerve injury.

METHODS: A total of 60 male Sprague-Dawley rats were randomly divided into three groups (n=12): normal control group, dexmedetomidine group and saline group. Except for the normal control group, spared nerve injury model was established in the rats of dexmedetomidine group and saline group. Dexmedetomidine group was treated with intrathecal injection of dexmedetomidine 3 μg/kg every day within 14 days after injury. Saline group was given equal volume of saline for 14 days. The thermal withdrawal latency and mechanical withdrawal threshold were measured respectively before injury, after injury, before injection, and 2, 7, 14 days after intrathecal injection. Four rats were sacrificed in each group at day 2, 7 and 14 after injection, and the lumbar segments (L₄_-₆) of the spinal cord were removed. Real-time RT-PCR and western blot analysis were used to determine the expression of protein kinase C mRNA and protein in the spinal dorsal horn neurons.

Hematoxylin-eosin staining was performed to detect the morphology of the spinal dorsal horn neurons and immunohistochemistry staining was carried out to assess the expression level and distribution of protein kinase C.

RESULTS AND CONCLUSION: The thermal withdrawal latency and mechanical withdrawal threshold in dexmedetomidine group and saline group were significantly decreased compared with normal control group before or after injection (P < 0.05). However, both the thermal withdrawal latency and mechanical withdrawal threshold in dexmedetomidine group after intrathecal injection were significantly higher than those in saline group (P < 0.05). The protein kinase C expression in spinal dorsal horn neurons was significantly decreased in dexmedetomidine group compared with saline, and reached to the most lowest levels as normal control group on 14 days after injection. Moreover, the apoptosis of spinal dorsal horn neurons in dexmedetomidine group was lighter than that in saline group, and was similar to the morphology of neurons in normal control group on 14 days after injection. Intrathecal injection of dexmedetomidine could attenuate the hyperalgesia induced by spared nerve injury, which might be associated with the inhibition of protein kinase C expression in spinal dorsal horn.

中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

全文链接：

Key words: spinal cord, neuralgia, protein kinase C

CLC Number:

R318

Deng Hai-hong, Ma Song-mei, Xiao Xiao-shan. Effect of intrathecal injection of dexmedetomidine on protein kinase C expression of spinal dorsal horn neurons in a rat model of chronic neuralgia[J]. Chinese Journal of Tissue Engineering Research, 2014, 18(29): 4683-4688.

Figures/Tables 2

2.1 实验动物数量分析实验分批进行，脱落动物在下一批随机分组补充。总共饲养69只SD大鼠，60只纳入实验，9只不纳入实验统计：鞘内置管后死亡2例，出现神经病理性损伤感觉和运动丧失5例，导管脱落2例。 2.2 三组大鼠痛阈的变化造模前3组大鼠热刺激缩足反射潜伏期、机械刺激缩足反射痛阈值差异无显著性意义。与正常对照组比较，给药前和给药后各时点生理盐水组和右美托咪定组热刺激缩足反射潜伏期、机械刺激缩足反射痛阈值均明显缩短(P < 0.05)。与生理盐水组比较，右美托咪定组在给药后各时点热刺激缩足反射潜伏期、机械刺激缩足反射痛阈值均明显延长(P < 0.05)，见表1。 2.3 光镜下各组脊髓病理学变化正常对照组神经元细胞未见明显病理改变；生理盐水组脊髓背角神经元数目明显减少，部分细胞出现皱缩、胞核轮廓不清，甚至变性坏死，细胞内尼氏体聚集成团块状或溶解消失；右美托咪定组在给药前脊髓背角神经元变性坏死及尼氏体凝固、溶解情况与生理盐水组相似，但随着给药天数的增加逐渐减轻，直至14 d接近正常(图1)。 2.4 各组蛋白激酶C mRNA表达水平变化 RT-PCR检测结果显示，与正常对照组相比，生理盐水组蛋白激酶C mRNA表达水平明显升高(P < 0.05)，而右美托咪定组在给药后第2天其表达水平明显低于生理盐水组，并随着给药天数的增加继续降低，到14 d其表达水平接近正常对照组，低于生理盐水组(P < 0.05)，见图2。 2.5 Western blot检测各组蛋白激酶C蛋白表达水平 Western blot显示，正常对照组蛋白激酶C蛋白表达较低，但生理盐水组表达明显升高(P < 0.05)，给药2 d后右美托咪定组蛋白激酶C表达有所下降，随着给药时间的延长，右美托咪定组蛋白激酶C表达持续下降，在14 d时达到最低，与正常对照组表达相当，7，14 d时与生理盐水组相比差异有显著性意义(P < 0.05)，见图3。 2.6 免疫组织化学各组蛋白激酶C蛋白表达比较正常对照组脊髓背角神经元蛋白激酶C蛋白表达为阴性或弱阳性；生理盐水组脊髓背角神经元中蛋白激酶C表达为强阳性；右美托咪定组神经元术后蛋白激酶C表达为强阳性，随着给药天数的增加，其表达逐渐降低，到14 d表达接近阴性(图4)。 "

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