中文摘要：

目的：观察右美托咪定（DEX）对烧伤疼痛大鼠的镇痛作用和P2X3受体在外侧中脑导水管周围灰质（l PAG）表达的影响。方法：SD大鼠随机分为正常组、假烧伤组、烧伤组、烧伤＋DEX1组及烧伤＋DEX2组,DEX1组和DEX2组分别给予腹腔注射10μg和30μg DEX;von Frey纤维检测大鼠机械痛阈,免疫组化检测大鼠在烧伤前后及注射DEX后l PAG中P2X3受体表达变化;观察l PAG中微量注射P2X3受体拮抗剂A-317491对DEX镇痛作用的影响。结果：烧伤疼痛大鼠机械痛阈下降;腹腔注射DEX后烧伤疼痛大鼠机械痛阈升高伴l PAG中P2X3受体表达上调。l PAG微量注射P2X3受体特异性拮抗剂A-317491后可部分翻转DEX的镇痛作用。结论：腹腔注射DEX通过上调烧伤疼痛大鼠l PAG中P2X3受体表达,增强机体内源性下行镇痛系统的作用,对烧伤疼痛产生镇痛作用。

英文摘要：

Objective： To observe the possible analgesic effect and the change of expression of P2X3 receptor in the lateral midbrain periaqueductal gray（l PAG） after intraperitoneal injection of dexmedetomidine（DEX）, a specific agonist of α2-adrenergic receptor, in second degree burn model in rats. Methods： Sprague-Dawley（SD）rats were randomly divided into 5 groups： normal group, sham-burn group, burn group, burn plus DEX1 group and burn plus DEX2 group. The burn plus DEX1 group and burn plus DEX2 group rats were administered DEX 10 μg and 30 μg respectively. Electronic von Frey filaments were used to determine mechanical withdrawal threshold（MWT）in rats. Expressions of P2X3 receptor in the IPAG of burned and DEX-treated rats were detected by using immunohistochemical technique. The effect of intra-l PAG injection of A-317491, a selective antagonist of P2X3 receptor, on DEX analgesic action was also studied. Results： The MWT Values were decreased in burned rats. Intraperitoneal injection of DEX increased MWT values and the expression of P2X3 receptors in the l PAG of burned rats. The l PAG microinjection of A-317491 partially but significantly blocked analgesic effect of DEX. Conclusion： Intraperitoneal injection of DEX can increase the MWT values and up-regulate the P2X3 receptor expression in the l PAG in burned rats, thereby enhancing the function of the central endogenous pain control system and alleviate the burn pain.