小剂量氯胺酮抑制慢性神经痛大鼠大脑皮质P2X4受体表达

Small-dose Ketamine Inhibit the Expression of P2X4 Receptor in Cerebral Cortex of the 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大脑皮质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3 d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(10 mg/kg),CCI组腹腔注射等量的生理盐水,给药至术后7 d。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1 d、术后1、3、7 d用热辐射法测定TWL;术后7 d用免疫组织化学法检测大鼠大脑皮质P2X4受体的表达。结果术前1 d三组大鼠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。与术前及CCI组及假手术组相比,氯胺酮治疗组术后3 d始TWL呈进行性下降,以术后7 d为甚(P<0.05);术后7 d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大脑皮质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大脑皮质P2X4受体表达有关。

Objective To observe the effect on thermal hyperalgesia and expression of P2X4receptor in cerebral cortex by continuous intraperitoneal injecting low dose ketamine to CCT rats,meanwhile,to explore the potential role that P2X4receptor may play in neuropathic pain.Methods 24 Sprague-Dawley rats were randomly divided into 3 groups（n=8）： group S（sham group）,group C： CCI＋normal saline;group K： CCI＋ketamine（10mg/kg）.Thermal withdrawal latency（TWL） were determined by thermal radiation apparatus 1 days before the operation and 1,3,7days after the operation respectively;After 3 days,thermal hyperalgesia was determined by examining TWL,then the CCI rats were intraperitoneal injected normal saline、ketamine respectively.The expression of P2X4receptor were assessed 7 days after the operation using immunohistochemistry.Results Compared with the pre-operation,the TWL in group S decreased slightly.Compared with the pre-operation and group S,TWL in group C,group K was significantlyincreased after 3 days of the operation（P〈0.05）,especially on 7 days.TWL in group K elevated significantly compared with group C on 7 days after the operation（P〈0.05）.Compared with group S,expression of P2X4receptor of group C,K were increased significantly on 7 days after operation（P〈0.01）.especially in group K（P〈0.05）.Most of the P2X4receptor positive cells displayed the form of activated microglia.Conclusion Small dose of intraperitoneal injecting ketamine can release hyperalgesia symptom of rats,partly because of inhibiting the expression of P2X4 receptor on cerebral cortex,inferred that the analgesic effect of ketamine is achieved at least by inhibiting the expression of P2X4 receptor directly or indirectly.