鞘内注射吗啡加可乐定对切口痛大鼠脊髓背角蛋白激酶A催化亚单位表达的影响

目的 观察鞘内注射(intrathecal injection,IT)吗啡加可乐定对切口痛大鼠脊髓背角蛋白激酶A(protein kinaseA,PKA)催化亚单位表达的影响.方法 选择鞘内置管成功的雄性SD大鼠80只,随机分为5组,每组16只,分别为假手术组、对照组、吗啡2.5μg组、可乐定5 μg组和吗啡2.5 μg+可乐定5μg组.按Yaksh法鞘内置管,按Brennan法制作大鼠足底切口疼痛模型,用机械缩爪反射阈值(mechanical withdrawal threshold.MWT)和热缩爪潜伏期(thermal withdrawal latency,TWL)观察疼痛行为学变化,应用免疫组织化学法和免疫印迹法测定大鼠脊髓背角PKA催化亚单位表达的变化.结果 与假手术组比较,术后2h对照组大鼠的MWT明显降低,TWL明显缩短(P<0.01),脊髓背角PKA催化亚单位免疫反应阳性神经元数量和神经元胞浆内PKA催化亚单位表达明显增加(P<0.01);与对照组比较,吗啡2.5μg+可乐定5μg组大鼠的MWT明显增加,TWL明显延长(P<0.01),脊髓背角PKA催化亚单位免疫反应阳性神经元数量和神经元胞浆内PKA催化哑单位表达明显减少(P<0.01);而吗啡2.5μg组和可乐定5μg组大鼠的MWT、TWL、脊髓背角PKA催化亚单位免疫反应阳性神经元数量和神经元胞浆内PKA催化亚单位表达与对照组比较均无统计学意义.结论 在大鼠切口痛模型中,IT可乐定能增强吗啡的抗伤害作用,其机制可能与其抑制切口痛引起的脊髓背角PKA催化亚单位的表达增加有关.

Effect of intrathecal morphine plus clonidine on expression of protein kinase A catalytic subunit in the spinal dorsal horn in a rat model of incisional pain

Objective To observe the effect of intrathecal clonidine plus morphine on expression of protein kinase A (PKA) catalytic subunit in the spinal dorsal horn in a rat model of incisional pain. Methods Eighty male Sprague-Dawley rats were divided randomly into five groups: sham group, control group, pre-incisional morphine 2.5 μg group, pro-incisional clonidine 5 μg group and preincisional morphine 2.5 μg plus clonidine 5 lag group (n=16). lntrathecal catheter and the model of incisional pain were pro-duced according to Yaksh and Brennan's described method respectively. Changes of pain behavior were assessed by mechanical with-drawal threshold (MWT) and thermal withdrawal latency(TWL). The expressions of PKA catalytic subunit in the spinal dorsal horn were assessed by immunohistochemical method and western blotting analysis. Results Compared with sham group, MWT and TWL in control group were decreased significantly at 2 h after incision (P<0.01) and the number of positive cells and protein expression of PKA catalytic subunit in the spinal dorsal horn were increased significantly in control group (P<0.01). Compared with control group, MWT and TWL in pre-incision morphine 2 μg plus clonidine 5 lag group were increased significantly at 2 h after incision (P<0.01) and the number of positive cells and protein expression of PKA catalytic subunit in the spinal dorsal horn were decreased significantly in pre-incision morphine 2 μg plus clonidine 5 μg group (P<0.01). However, MWT, TWL and the number of positive cells and pro-tein expression of PKA catalytic subunit in the spinal dorsal horn changed with no statistical significance in pre-incisional morphine 2.5 μg group and pre-incisional clonidine 5 μg group compared with control group. Conclusion lntrathecal clonidine significantly enhances the antinociceptive effect of intrathecal morphine in a rat model of incisional pain, which might be associated with inhibi-tion of the increased expression of PKA catalytic subunit in spinal cord.