L-精氨酸促进背根神经节NO合成对糖尿病大鼠机械性痛敏的影响

Effects of L-Arginin promotion on nitric oxide expression on mechanical hyperalgesia in diabetic rats

目的研究L-精氨酸减轻糖尿病大鼠机械性痛敏的作用及可能的机制。方法36只成年雄性SD大鼠随机分为3组(n=12):正常对照组(CON组)、糖尿病组(DM组)、L-精氨酸(L-Arginin)干预组(L-Arg组)。糖尿病大鼠成模后L-Arg组第1天腹腔注射L-Arginin 300 mg/kg,每日1次,持续14 d。DM组第1天腹腔注射等剂量生理盐水,每日1次,持续14 d。CON组在相同时间点腹腔注射等剂量生理盐水,每日1次,持续14 d。测定L-arginin注射前(T_0)、注射后14 d(T_1)、21 d(T_2)、28 d(T_3)测定大鼠机械缩足阈值(paw mechanical withdrawal threshold,PMWT)。L-Arginin注射后28 d采用硝酸还原酶法测定背根神经节中一氧化氮(nitrogen monoxidum,NO)含量、免疫组化法测定背根神经节降钙素基因相关肽(calcitonin gene-related peptide,CGRP)表达。结果T_0时间点,DM组PMWT相对于CON组明显降低,在T_1、T_2、T_3时间点较CON组进一步降低(P<0.05)。L-Arg组在T_1、T_2、T_3时间点相对于DM组PMWT升高(P<0.05)。DM组背根神经节NO含量较CON组明显减少,L-Arg组背根神经节NO表达相对DM组明显增加(P<0.05)。DM组背根神经节CGRP阳性颗粒表达较CON组减少,给予L-Arginin后背根神经节CGRP表达相对与DM组明显增加(P<0.05)。结论糖尿病大鼠机械性痛敏增强可能与背根神经节NO和CGRP表达下调有关,L-Arginin可明显促进背根神经节NO合成及CGRP表达,可能是其减轻机械性痛敏机制之一。

Objective To investigate the role and possible mechanisms of L-Arginin in reducing mechanical hyperalgesia in diabetic rats. Methods Male SD rats were divided into 3 groups randomly （n=12）： normal group （CON）, diabetic mellitus group （DM）, L-Arginin intervention group （L-Arg）. L-Arginin （300 mg/kg） was injected intraperitoneally once a day for 2 weeks consecutively in L-Arg group DM rats. The same volume of normal saline was injeceted once a day for 2 weeks in rats of DM group and in CON group at the same time. Paw mechanical withdrawal threshold （PMWT） was measured before L-Arginin injection（T0）and after 14 d（T1）, 21 d（T2）, 28 d （T3） of L- Arginin injections. After 28 d of L-Arginin injection, nitrogen monoxide （NO） content and calcitonin gene-related peptide （CGRP） in dor＇q root ganglion were determined by nitrate reductase method and immunohistochemistry respectively. Results PMWT were significantly decreased at To, Tb T2 and T3 in DM group than that in CON group （P〈0.05）. PMWT in group L-Arg were increased at T~, T2 and T3 compared with that in DM group （P〈0.05）. The levels of NO and CGRP in dorsal root ganglion were decreased in DM group than that in CON group （P〈0.05）. Injection of L-Ariginin increased NO content as well as the level of CGRP in dorsal root ganglion （P〈0.05）. Conclusion Mechanical hyperalgesia in diabetic rats may be related with the reduction of NO and CGRP expression in doral root ganglion. L-Arginin can significantly promote the synthesis of NO and the CGRP expression in dorsal root ganglion, which may be one of the mechanisms to reduce mechanical hyperalgesia.