神经病理性疼痛大鼠鞘内注射SB203580的镇痛作用

Analgesic effect of intrathecal SB203580 in a rat model of neuropathic pain

目的观察神经病理性疼痛大鼠鞘内注射p38丝裂原活化蛋白激酶(p38MAPK)抑制剂 SB203580的镇痛作用,探讨p38MAPK信号转导通路在慢性神经病理性疼痛中的作用。方法雄性 SD大鼠,体重220-250 g,建立坐骨神经结扎性损伤(CCI)疼痛模型,第一部分 40只CCI大鼠,随机分为5组,对照组、SB0．1μg组、SB0．5μg组、SB2．5μg组和SB5μg组,(n=8),CCI后7 d,鞘内注射2％二甲基亚砜或不同剂量的SB203580(0．1、0．5、2．5、5μg)10μl,在给药前和给药后0．5、3、6、12、24 h用 von Frey丝测定大鼠术侧后爪机械缩足反射阈值(MWT);另外36只大鼠,随机分为6组(n=6):Sham 组、CCI组、DMSO组、SB0．1、0．5、5μg组,CCI后7 d鞘内注射相应剂量SB203580 10μl,给药后6h取L4,5 脊髓,用免疫组织化学方法检测脊髓背角磷酸化环磷酸腺苷反应元件结合蛋白(pcREB)的表达。结果 CCI后大鼠产生了机械痛敏,鞘内注射SB203580剂量依赖性地提高了MWT。CCI后脊髓背角 pCREB阳性神经元增加,鞘内注射SB 0．5、5μg抑制了CCI引起的脊髓背角pCREB表达增加(P< 0．01)。结论鞘内注射SB203580能减轻CCI引起的痛敏,抑制脊髓背角CREB的磷酸化,p38MAPK 信号通路参与慢性神经病理性疼痛。

Objective To investigate the analgesic effect of a specific p38MAPK inhibitor SB203580 in a rat model of chronic constriction injury （CCI） to sciatic nerve. Methods Male SD rats weighing 220-250 g were used in this study. The neuropathie pain model was established by CCI to sciatic nerve. The rats were anesthetized with intraperitoneal （ i. p. ） pentobarbital 40 mg · kg^- 1 . Left sciatic nerve was exposed and 4 loose ligatures were placed on left sciatic nerve at 1 mm intervals with 4-0 silk suture. The animals were allowed 7 days to recover from surgery. Intratheeal （IT） SB203580 was given through a needle inserted at L5.6 interspace. In experiment A, 40 rats wee randomly divided into 5 groups （ n = 8 each） ： control group and 4 SBgroups （SB203580 0. 1, 0.5, 2.5 and 5.0 μg were given respectively）. Response of the hindpaw to mechanical stimulation with yon Frey filament （MWT） was measured before （To ,baseline） and at 0.5, 3, 6, 12 and 24 h （T1-5） after IT SB203580 injection. In experiment B, 36 animals were randomly divided into 6 groups （n = 6 each）： （1） sham operation group; （2） CCI group; （3） DMSO group; （4） SB 0.1 μg group; （5） SB 0.5 μg group and （6） SB 5.0 μg group. The animals were killed at 6h after IT SB203580 administration and L5.6 lumbar segment of the spinal cord was removed for determination of pCREB expression in the dorsal horn by immuno-eytoehemistry. Results The rats developed hyperalgesia after CCI and IT SB203580 administration significantly increased MWT in a dose dependent manner. The number of pCREB positive neurons in the L4,5 spinal dorsal horn was significantly increased after CCI. Intertheeal administration of SB203580 0.5 or 5.0 μg significantly inhibited the CCI-indueed increase in pCREB expression. Conclusion Intratheeal administration of SB203580 can attenuate the hyperalgesia induced by CCI and inhibition of CREB phosphorylation in the spinal dorsal horn is involved in the mechanism.