Objective: To investigate the role of intrathecal injection of metabotropic glutamate receptor 5 (mGluR5) antisense oligodeoxynucleotide (ODN) on the occurrence of morphine tolerance and expressions of spinal G proteins in rats. Methods: Forty-eight male Sprague-Dawley rats were randomly divided into six groups: control group (S group, n = 14), antisense ODN group (ANT group, n = 6), mismatch ODN group (MIS group, n = 6), morphine tolerance group (M group, n = 8), antisense ODN plus morphine group (AM group, n = 8) and mismatch ODN plus morphine group (MM group, n = 8). Rats in ANT group, MIS group, AM group and MM group received 5 ul of intrathecal 30 nM ODN twice a day for 5 days. Rats in S and M groups were received 5μl of 0.9% saline twice a day for 5 days. On day 6, real-time PCR was used to investigate the mRNA of mGluR5 in S group, ANT group and MIS group. From day 6, 15μg morphine was added twice a day in M group, AM group and MM group. Rats in S group received 5 μl of 0.9% saline instead of any drugs. Hot-plate test and paw pressure test were used to assess nociception and maximum percent effect (MPE) was measured. The expressions of G proteins (Gai, Gao, Gaq and GP) were detected by western blot. Results: Compared with S group, mGluR5 was reduced by 48.2% in ANT group (P ＜ 0.05). MPE% of M group and MM group decreased on day 8, with no significant difference with S group (P＞ 0.05). MPE% of AM group on day 8 was still higher than S group (P ＜ 0.05). MPE% of AM group on day 7 and 8 was higher than M group (P ＜ 0.05). The expressions of G proteins (Gai, Gao, Gaq and GP) in M group and MM group were up-regulated, as compared with S group (P ＜ 0.05). The expressions of G proteins between AM and S groups were no significantly different (F ＞ 0.05). The expression of G protein of AM group was decreased than M group. Conclusion: Intrathecal injection of mGluR5 antisense ODN can inhibit the occurrence of morphine tolerance, and reduce the up-regulated G protein (Gai, Gao, Gaq and GP) expression in the rat spinal cord which would happen when tolerance occurs.%目的:研究鞘内注射代谢型谷氨酸5受体(metabotropic glutamate receptor 5,mGluR5)反义寡聚脱氧核苷酸(oligodeoxynucleotide,ODN)时大鼠吗啡耐受发生情况及其对脊髓内G蛋白各亚型表达的影响.方法:将48只雄性SD大鼠随机分为6组:对照组(S组,n=14),反义链组(ANT组,n =6),错义链组(MIS组,n=6),吗啡耐受组(M组,n=6),反义链吗啡合用组(AM组,n=8)和错义链吗啡合用组(MM组,n=8).采用鞘内给药方式注射寡聚核苷酸、吗啡和生理盐水.以5μl含30 nM的寡聚核苷酸(ANT组,MIS组,AM组和MM组)或0.9％生理盐水(S组和M组)每日给药2次,连续5天.于第6天取6只S组及ANT组和MIS组大鼠L4/5脊髓行real-time PCR,观察其mGluR5的mRNA表达.其余大鼠于第6天起连续3天每日给吗啡2次,每次15 μg,S组以5 μl 0.9％生理盐水代替.给药后以热板试验测定其热痛阈,以缩爪阈值作为机械痛阈指标,并计算最大效应分数(maximum percent effect,MPE)进行比较.采用免疫印迹(western blot)方法检测并比较各组L4/5脊髓中G蛋白各亚型(Gαi,Gαo,Gαq和Gβ)的表达.结果:ANT组中mGluR5含量比S 组下降48.2％ (P＜0.05),MIS组无此效果.M组和MM组大鼠MPE％在第8天与S组比较无统计学差异(P＞0.05),AM组大鼠MPE％在第8天仍高于S组,有统计学意义(P＜0.05).AM组大鼠MPE％在第7～8天即显著高于M组(P＜0.05).第9天M组和MM组大鼠Gαi,Gαo,Gαq和Gβ 的蛋白表达量显著高于S组(P＜0.05).而AM组大鼠G蛋白各亚型表达量均与S组无显著性差异(P＞0.05),与M组相比显著下调(P＜0.05).结论:大鼠吗啡耐受发生时,大鼠腰段脊髓G蛋白各亚型表达均明显升高.鞘内注射mGluR5反义寡聚脱氧核苷酸能显著抑制大鼠吗啡耐受的发生并抑制G蛋白各亚型的表达升高.
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