小剂量氯胺酮抑制慢性神经痛大鼠脊髓背角P2X4受体表达

Low-dose ketamine inhibits expression of P2X_4 receptor in spinal dorsal horn of rats with chronic neuropathic pain

目的:观察小剂量氯胺酮腹腔注射对慢性坐骨神经收缩损伤(CCI)大鼠的镇痛效应及其对大鼠脊髓背角P2X4受体表达的影响,探讨其可能的镇痛机制。方法:24只SD大鼠随机分为假手术组、CCI组及氯胺酮治疗组(n=8)。CCI组及氯胺酮治疗组大鼠均制备慢性坐骨神经痛CCI模型;术后3d测定热缩足反射潜伏期(thermal withdrawal latency,TWL)确定痛觉过敏形成后,氯胺酮治疗组大鼠腹腔注射小剂量氯胺酮(10mg·kg-1),CCI组腹腔注射等量的生理盐水,给药至术后7d。假手术组大鼠单纯坐骨神经暴露,不用肠线结扎,也不给药治疗。分别于术前1d、术后1、3、7d用热辐射法测定TWL;术后7d用免疫组织化学法检测大鼠腰段脊髓P2X4受体的表达。结果:术前1d,3组大鼠TWL无统计学差异;假手术组术后术侧TWL轻度下降,但与术前相比无统计学差异。与术前、CCI组及假手术组相比,氯胺酮治疗组术后3d始TWL呈进行性下降,以术后7d为甚(P<0.05);术后7d氯胺酮治疗组TWL较CCI组显著升高(P<0.05),但仍低于假手术组(P<0.05)。与假手术组相比,CCI组及氯胺酮治疗组大鼠术侧脊髓背角P2X4受体表达显著增加(P<0.01);氯胺酮治疗组P2X4受体表达明显少于CCI组(P<0.05)。结论:小剂量氯胺酮腹腔注射可部分缓解慢性神经痛大鼠的痛觉过敏症状,可能部分与其直接或者间接抑制脊髓背角P2X4受体表达有关。

Objective： To observe the effect intraperitoneal injection of low dose ketamine on thermal hyperalgesia and expression of P2X4 receptor in spinal dorsal horn of rats with chronic constriction injury （CCI） of sciatic nerve,and to explore the potential role of P2X4 receptor in the neuropathic pain. Methods： Totally 24 Sprague-Dawley rats were randomly divided into 3 groups （n=8）： group S （sham group）,group C： CCI ＋ normal saline; and group K： CCI＋ketamine （10 mg· kg^-1）. Rat CCI model was used in the latter 2 groups. Three days after operation the thermal withdrawal latency （TWL） was determined to confirm the thermal hyperalgesia. Rats in group K were given low dose of ketamine （10 mg · kg^-1 ）and those in group C were given the same volume of normal saline for 7 days after operation. Animals in group S only had sciatic nerve exposed, with no ligation or drugs. TWL was determined 1 day before and 1,3,7 days after the operation. The expression of P2X4 receptor was assessed 7 clays after the operation using immunohistochemistry. Results： The TWL values were similar between the 3 groups before operation. The value in group S was slightly decreased after operation compared with before operation. Compared with the pre-operation,group S,and group C,the TWL value of group K began to gradually increase 3 days after operation till day 7 after operation（P（0.05）, On day 7 after operation, the TWL value was significantly higher than group C （P〈0.05）, but was still lower than that in group S （P〈0.05）. Immunohistoehemistry showed that the expression of P2X4 receptor in group C,K were significantly higher than that of group S （P〈0.01） ,and the expression in group K was significantly lower than that in group C （P〈0.05）. Conclusion： Intraperitoneal injection of ketamine can partly relieve the thermal hyperalgesia in rats with CCI of sciatic nerve,which might be related to the inhibition of P2X4 receptor expression in the spinal dorsal horn.