脊髓谷氨酸转运体、孤啡肽和脑源性神经营养因子在炎性痛大鼠吗啡耐受形成中的作用

Role of spinal cord glutamate transporter, orphanin FQ and brain-derived neurotrophic factor in the devel- opment of morphine tolerance in rats with inflammatory pain

目的探讨脊髓谷氨酸转运体（GT）、孤啡肽（OFQ）和脑源性神经营养因子（BDNF）在炎性痛大鼠吗啡耐受形成中的作用。方法健康雄性sD大鼠，8～10周龄，体重300～350g，取鞘内置管成功的雄性SD大鼠20只，采用随机数字表法，将其随机分为4组（n=5）：生理盐水组（Ns组）、炎性痛组（IP组）、吗啡组（M组）和GT激动剂riluzole组（R组）。Ns组于左后足踝关节腔注射生理盐水50μl，其余3组注射完全弗氏佐剂50μl。3d后，Ns组和IP组鞘内注射生理盐水10μl；M组鞘内注射吗啡10μg；R组鞘内注射riluzole10ptg，30min后注射吗啡10肛g。注射药物容量均为10μl，2次／d，连续7d。于鞘内给药前、鞘内给药2、4、6d和鞘内给药结束后1d（T0-4）时测定机械痛阈。于T4时痛阈测定后取左侧脊髓背角，采用RT-PCR法测定OFQmRNA和BDNFmRNA的表达。结果与Ns组比较，IP组机械痛阈降低，脊髓背角OFQmRNA及BDNFmRNA表达上调（P〈0．05或0．01）；与IP组比较，M组L1，2时机械痛阈升高，脊髓背角OFQmRNA及BDNFmRNA表达上调（P〈0．05或0．01），T3，4时机械痛阈差异无统计学意义（P〉0．05）；与M组比较，R组机械痛阈升高，脊髓背角OFQmRNA及BDNFmRNA表达下调（P〈0．05或0．01）。结论炎性痛大鼠长期注射吗啡时脊髓GT功能降低，导致谷氨酸水平升高和OFQ、BDNF表达上调之间的失衡，可能在吗啡耐受形成中起到一定作用。

Objective To investigate the role of spinal cord glutamate transporter （GT）, orphanin FQ （OFQ） and brain-derived neurotrophic factor （BDNF） in the development of morphine tolerance in the rats with in- tlammatory pain. Methods Twenty healthy male SD rats, aged 8-10 weeks, weighing 300-350 g, in which in- trathecal （IT） catheters were successfully placed, were randomized into 4 groups （ n = 5 each） ： normal saline group （group NS）, inflammatory pain group （group IP）, morphine group （group M） and riluzole （a GT agonist） group （group R）. NS 50 μl was injected into the ankle joint of the left hindlimb in group NS, while complete Freund＇s adjuvant 50μl was injected in the other three groups instead. After 3 days, groups NS and IP received IT NS 10 μl twice a day for 7 consecutive, days, group M IT morphine 10μg （10 /A） twice a day for 7 consecutive days, group R IT riluzole 10μg ＋ morphine 10μg （10 μl, at 30 min after riluzole administration） twice a day for 7 consecutive days. Mechanical pain threshold （MPT） was measured before IT administration and at day 2, 4, 6 of IT administration and 1 day after the end of IT administration （T0-4 ）.The animals were sacrificed after the last MPT measureinent, and the left spinal dorsal horns were isolated to detect the OFQ mRNA and BDNF mRNA expression by RT-PCR. Results Compared with group NS, MPT was significantly decreased and OFQ mRNA and BDNF mRNA expression was up-regulated in group IP （ P 〈 0.05 or 0.01 ）. Compared with group IP, MPT was significantly increased at T1,2 and OFQ mRNA and BDNF mRNA expression was up-regulated in group M （ P 〈 0.05 or 0.01）. There was no significant difference in MPT at T3.4 between groups IP and M （ P 〉 0.05）. Compared with group M, MPT was significantly increased and OFQ mRNA and BDNF mRNA expression was down-regulated in group R （P 〈0. 05 or 0.01 ）. Conclusion When the rats with inflammatory pain receive long-term injection of morphine, the tunction of spinal cord GT is decreased, resulting in increase in the glutamate level and up-regulation of OFQ and BDNF expression, and imbalance between the glutamate level, OFQ and BDNF expres- sion, which play a role in the development of morphine tolerance.