中文摘要：

目的：观察鞘内注射吗啡对背根神经节（DRG）神经元中P2X3受体的激活和表达的影响,同时探讨合并应用P2X3受体特异性抑制剂A-317491对大鼠鞘内吗啡耐受的影响。方法：鞘内置管成功的SD大鼠随机分为六组,每组7只：M3组,吗啡3天,每天单次鞘内给15μg/10μl吗啡,继而用10μl生理盐水冲管;M5组,吗啡5天（剂量及给药方式同前）;M7组,吗啡7天（剂量及给药方式同前）;M＋A组,A-317491合并吗啡7天,每天单次鞘内注射抑制剂A-317491（15μg/10μl）,30 min后给吗啡（15μg/10μl）,每次给药后用10μl生理盐水冲管;A组,A-317491 7天,每天单次鞘内给抑制剂A-317491（15μg/10μl）,继而用10μl生理盐水冲管,连续7天;S组,每天单次鞘内给20μl生理盐水。每次给药前及给药后30 min动态检测大鼠后肢50%缩爪阈值,以及热痛阈甩尾潜伏期,以评估吗啡耐受的发生。于给药后第8天测定痛阈后将大鼠处死,取L3-5节段背根神经节（DRG）进行蛋白印记和免疫荧光化学染色,观察DRG中P2X3的蛋白及免疫阳性细胞表达。结果：（1）鞘内给予P2X3受体特异性拮抗剂A-317491可明显延缓大鼠吗啡耐受的发展;（2）鞘内给予吗啡可致大鼠脊髓背根神经节中P2X3受体的表达呈时间依赖性的增加;3、慢性鞘内吗啡处理可激活DRG神经元中P2X3受体的表达,而给予A-317491后可以抑制这种表达的增加。结论：鞘内慢性吗啡处理可激活大鼠DRG神经元中的P2X3受体的表达,而选择性抑制P2X3受体可一定程度上抑制吗啡耐受的发生。

英文摘要：

Objective： To investigate the activation and expression of P2X3 receptor in the dorsal root ganglion（DRG） of rats with morphine tolerance. Methods： Forty-two male Sprague-Dawley rats weighing 200 - 250 g were randomly divided into six groups（7 in each）. Rats in group M3,M5,and M7 were intrathecally administrated 15 μg/10 μl morphine for 3,5, and 7 days, respectively; Rats in group（M＋A） were intrathecally administrated 15 μg/10 μl A-317491 plus 15 μg/10 μl morphine for seven days; Rats in group A were intrathecally administrated 15 μg/10 μl A-317491 for seven days; Rats in group S were intrathecally administrated 20 μl saline for seven days. All drugs were given once a day. The paw withdrawal and the tail flick tests were employed as behavior tests. The expression of P2X3 in the DRG was investigated with Western Blotting and immunofluorescence. Results：（1）Chronic morphine treatment for consecutive 7 days led to significant reduction of analgesic effect and pretreatment with the selective P2X3 receptor antagonist A-317391 attenuated morphine tolerance;（2）Western blotting and immunofluorescence results showed that the expression of P2X3 receptor was significantly increased in both small- and medium-sized DRG neurons. Conclusions： P2X3 receptor might be involved in the process of morphine anti-nociceptive tolerance and may be a new therapeutic target for the prevention of tolerance to morphine-induced anti-nociception.