鞘内注射肾上腺髓质素受体拮抗剂AM_(22-52)对吗啡耐受大鼠血浆及脊髓背角中氨基酸含量的影响

Effects of intrathecal AM_(22-52) on levels of amino acids of plasma and spinal dorsal horn in morphine tolerance rats

目的观察鞘内注射肾上腺髓质素(adrenomedullin,AM)受体拮抗剂AM22-52对吗啡耐受大鼠血浆及脊髓(L4-6)背角兴奋性氨基酸含量的影响,以探讨AM促成吗啡耐受形成的细胞学机制。方法♂SD大鼠,随机分为生理盐水组、吗啡组和吗啡+AM22-52组。以大鼠甩尾潜伏时评价疼痛行为,应用高效液相柱前衍生法测定血浆和脊髓背角氨基酸含量。结果连续7 d鞘内注射吗啡后,吗啡组大鼠甩尾反射潜伏时与生理盐水组比较,差异没有统计学意义,与吗啡组比较,吗啡+AM22-52组大鼠甩尾反射潜伏时明显增加(P<0.05～0.01);吗啡组大鼠血浆中Glu、Asp含量[Glu:(193.12±21.25)μmol·L-1,Asp:(37.40±7.13)μmol·L-1]明显高于生理盐水组(P<0.05-0.01),与吗啡组比较,吗啡+AM22-52组大鼠血浆中Glu含量(164.56±23.42)μmol·L-1有所降低,差异没有统计学意义,但Asp含量(18.02±2.87)μmol·L-1明显降低(P<0.05);吗啡组大鼠脊髓背角Glu(2.70±0.06)mol·g-1和Asp(2.48±0.12)mol·g-1的含量与生理盐水组比较明显升高(P<0.05),AM22-52联合注射后脊髓背角Glu、Asp含量分别为(2.33±0.16)mol·g-1和(1.94±0.11)mol·g-1,均明显低于吗啡耐受组(P<0.05)。结论鞘内注射AM受体拮抗剂AM22-52能抑制兴奋性氨基酸的释放,提示AM通过促进兴奋性氨基酸的释放,导致吗啡耐受。

Aim To investigate the effects of intrathecal （ i. t. ） administration of AM22-52 , a AM receptor antagonist, on the release of excitatory amino acids （EAAs） in plasma and spinal dorsal horn in morphine tolerance rats. Methods SD rats were randomly divided into saline group, morphine group and morphine ＋ AM22-52 group. Tail flick latency （TFL） was used to characterize noxious pain of rats. High performance liquid chromatography-fluorescence detector （HPLC- FLD） was used to measure the concentration of amino acids. Results After i.t. AM22-52 7 days, no significant change in TFL was seen between morphine and saline group. However, compared with morphine group, morphine ＋ AM22-52 group TFL was increased significantly （P 〈 0.05 - 0.01 ）. Concentrations of Glu and Asp （ Glu ：193.12± 21. 25 μmol· L^-1, Asp：37.40 ± 7. 13 μmol · L^-1 ） in plasma were increased significantly in morphine group as compared with those in saline group（P 〈0.05 -0.01）. Asp（18.02 ±2.87） μmol · L^-1 in plasma was significantly decreased in morphine ＋ AM22-52 group （P 〈 0.05） as compared with morphine group, but Glu （ 164. 56 ±23.42） μmol · L^-1 was not significantly decreased. Glu and Asp （Glu：2.70±0.06 mol · g^-1, Asp： 2.48±0.12mol · g^-1） in spinal dorsal horn were significantly increased in morphine group as compared with those in saline group （P 〈 0.05 ） , while, Glu and Asp （ Glu ： 2. 33 ±0.16 mol· g^-1, Asp： 1.94±0.11mol·g^-1）in spinal dorsal horn in morphine ＋ AM22-52 group were both lower than those of morphine group （P 〈 0. 05）. Conclusion The present study demonstrates that pre-administration of AM22-52 effeetively inhibits the release of EAAs in plasma and spinal dorsal horn of morphine tolerance rats. It indieates that the meehanism of AM involved in the development of morphine toleranee may be relevant to the induction of the release of EAAs.