Objective To investigate the effects of rapamycin on neuropathic pain and apoptosis of neurons in the spinal cord of rats after spinal nerve ligation. Methods Thirty male SD rats were randomly divided into three groups(n = 10):sham group,spinal nerve ligation group(SNL group)and rapamycin group(Rap group). After intrathecal catheter implantation between L4 - 5 vertebrae, the rats in SNL group and Rap group underwent L5 spinal nerve ligation. The surgical procedure in sham group was identical except nerve ligation. The rats were injected with rapamycin(0. 1 μg/ 10 μl)per day for 7 d via intrathecal catheter in Rap group after L5 spi-nal nerve ligation,while the rats were injected intrathecally with the same volume of vehicle(5% DMSO)in sham group and SNL group. Paw withdrawal threshold(PWT)and paw withdrawal latency(PWL)were measured at 1,3,5,and 7 d after surgery. At day 7 after surgery,the rats were sacrificed. Ipsilateral L5 spinal cord dorsal horn was examined using transmission electron microscope. Expression of LC3,NeuN and a - caspase3 in the L5 cord dorsal horn were measured by Western blot. Results Compared with sham group,PWT and PWL of rats were significantly decreased at 1,3 day after SNL in SNL group,respectively,and lasted for 7 d(P <0. 05). At day 7 after SNL,PWT[(12. 5 ± 1. 0)g]and PWL[(7. 8 ± 0. 4)s]were decreased by 67% and 44%,respectively(P <0. 05),the levels of LC3 Ⅱ and a - caspase3 expression increased by 96% and 359%,respectively(P < 0. 05),while the levels of NeuN expression decreased by 21% . Compared to SNL group,PWT and PWL of rats were significantly increased in Rap group(P <0. 05). At day 7 after SNL,PWT[(24. 9 ± 1. 6)g]and PWL[(11. 8 ± 0. 8)s]were increased by 99% and 51%,respectively(P <0. 05),the levels of LC3 Ⅱ and NeuN expression increased by 44% and 19%,respectively(P < 0. 05),while the levels of a -caspase3 expression decreased by 27%(P < 0. 05). More autophagosomes were found in Rap group than in SNL group. Conclusion Intrathecal rapamycin may ameliorate SNL-induced neuropathic pain by increasing the autophagy and inhibiting the apoptosis of neu-rons.%目的 研究鞘内注射雷帕霉素对大鼠神经病理性疼痛及脊髓背角神经元凋亡的影响.方法 雄性SD大鼠30只随机分为假手术组(sham组)、脊神经结扎组(SNL组)和雷帕霉素组(Rap组),每组10只.各组大鼠L4-5鞘内置管后,SNL组和Rap组大鼠结扎左侧腰5脊神经建立神经病理性疼痛模型,sham组大鼠则仅分离暴露左侧腰5神经.Rap组大鼠于术后30 min鞘内注射雷帕霉素0.1μg/10μl,sham组和SNL组则给予注射等容溶剂(5%DMSO).每日1次,连续7 d.各组大鼠测量术后1,3,5,7 d机械痛阈(paw withdrawal threshold,PWT)和热痛阈(paw withdrawal latency,PWL).术后第7天处死大鼠并立即取左侧L5节段脊髓背角,电镜下观察神经元自噬体(n=3);Western blot法检测自噬相关蛋白LC3、神经元特异性蛋白NeuN以及凋亡相关蛋白a-caspase3表达(n=7).结果 与sham组比较,SNL组大鼠PWT和PWL在术后第1天和第3天开始分别明显降低,且持续到术后第7天(P<0.05),术后第7天PWT、PWL分别为(12.5±1.0)g和(7.8±0.4)s,较sham组分别降低67%和44%(P<0.05);而脊髓背角LC3Ⅱ和a-caspase3表达分别增高96%和359%(P<0.05),NeuN表达降低21%(P<0.05);与SNL组比较,Rap组大鼠各相应时间点PWT和PWL明显增高(P<0.05),术后第7天PWT、PWL分别为(24.9±1.6)g和(11.8±0.8)s,较SNL组分别增加99%和51%(P<0.05);而脊髓背角LC3Ⅱ和NeuN表达增高44%和19%(P<0.05),a-caspase3表达降低27%(P<0.05).电镜下Rap组脊髓背角神经元自噬体较SNL组可见较多自噬体.结论 雷帕霉素能减轻神经病理性疼痛,其机制可能与雷帕霉素增加脊髓背角神经元自噬,减少神经元凋亡有关.
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