支链氨基酸和相关拮抗剂降低大鼠中枢5-羟色胺合成减轻术后疲劳综合征的研究

Synthesis reduction of central neurotransmitter 5-hydroxytryptamine by branched chain amino acid and associated antagonists improves postoperative fatigue syndrome

目的：研究观察支链氨基酸（BCAA）和相关拮抗剂作用于中枢5-羟色胺（5-HT）代谢通路后大鼠术后疲劳的改变情况，并探讨5-HT在术后疲劳综合征（POFS）发生发展中的作用。方法50只SD大鼠随机分为5组，每组10只，对照组分别为假手术组和模型组（均注射生理盐水）；干预组分别为注射中性氨基酸转运体抑制剂（BCH）的BCH组、注射5-HT重摄取抑制剂氟西汀的氟西汀组和注射BCAA（缬氨酸、亮氨酸、异亮氨酸以5∶3∶2比例的混合液）的BCAA组。除假手术组仅开腹翻动肠袢外，其余各组行70％中段小肠切除端端吻合术。各组术前1 h、术后1、2、3、4 d腹腔注射给药，每天1次。观察手术前后各组大鼠的一般情况；术后第1～7天分别进行Morris水迷宫试验（包括隐藏平台获得试验和空间搜索试验）以检测大鼠学习记忆能力和鼠尾悬吊试验（检测大鼠体力耐力）评估大鼠疲劳程度；术后第8天采用高效液相色谱-荧光检测器检测大鼠脑组织（海马、纹状体及下丘脑）中的色氨酸、5-HT及5-羟吲哚乙酸（5-HIAA）的水平。结果与模型组相比，干预组大鼠一般情况较好，术后疲劳程度减轻。在隐藏平台获得试验中，模型组穿越平台次数最少，与其他4组比较，差异有统计学意义（P＜0．05）；模型组与BCAA组的潜伏时间最长，与假手术组和BCH组比较，差异也有统计学意义（P＜0．05）；在空间搜索试验中，模型组与BCAA组的穿越平台次数最少，模型组潜伏期时间与干预组比较差异无统计学意义（P＞0．05）。鼠尾悬吊试验显示，BCH组和BCAA组大鼠体力耐力较模型组和氟西汀组更好（P＜0．05）。高效液相-荧光检测法检测，3个干预组的脑组织色氨酸水平均明显低于模型组（P＜0．01）；模型组海马5-HT水平高于BCH组和氟西汀组（P＜0．05）；纹状体中5-HT水平比较，假手术组最低，模型组与干预组差异无统计学意义（P＞0．05）；模型组下丘脑5-HIAA含量高于氟西汀组（P＜0．05），但与BCH组和BCAA组比较，差异无统计学意义（P＞0．05）。结论 BCAA以及相关拮抗剂BCH和氟西汀，能降低大鼠神经中枢对色氨酸的摄取，减少大脑5-HT合成，改善大鼠POFS。

Objective To observe the change of postoperative fatigue in rats after the effect of branched chain amino acid （BCAA） and associated antagonists on central neurotransmitter 5-HT metabolic pathway, and to investigate the role of 5-HT in the development of postoperative fatigue syndrome （POFS）. Methods Fifty SD rats were randomly divided into sham operation group （C group, n=10）, model group （M group, n=10）, L-type amino acid transporter inhibitor group （L group, n=10）, 5-HT uptake inhibitor group （F group, n=10） and branched chain amino acids （B group, n=10）. The rats in the C group and the M group were injected with normal saline, while other three groups were respectively injected with BCH, fluoxetine, BCAA（val∶leucine∶isoleucine=5∶3∶2）, on preoperative 1 h, postoperative day 1, 2, 3, 4. The rats, except for those in the C group, underwent resection of 70% of the middle small intestine with end-to-end anastomosis. General status of the rats was observed before and after surgery. Morris water maze test, including the hidden platform test and search space test （detecting the learning ability of rats） and tail suspension test （detecting physical endurance of rats） were used to evaluate the degree of POFS from postoperative day 1 to day 7. Concentration of tryptophan （TRP）, 5-HT, 5-hydroxyindoleacetic acid （5-HIAA） in different position of brain （hippocampus, striatum, hypothalamus） of rats were measured by high performance liquid chromatography（HPLC） at postoperative day 8. Results As compared to the M group, other four groups showed better general condition and less fatigue. In the hidden platform test, M group showed the least time of crossing platform as compared to other four groups （all P〈0.05）. Meanwhile, M group and B group performed the longer incubation period than C group and L group （all P〈0.05）. In search space test, M group and B group showed less time of crossing platform, but there were no significant differences among the groups （all P〉0.05）. In tail suspension test, M group and F group showed lower score of physical strength than L group and B group（all P〈0.05）. Levels of TRP in the L, F, B groups were lower compared to the M group （all P〈0.01） in brain tissue. The least concentration of striatum 5-HT was found in the C group but there were no significant differences among the M, L, F and B groups. Level of 5-HIAA in the M group, only in hypothalamus, was higher than that in the F group （P〈0.05）, but no significant differences between the M group and the L and B groups were found. Conclusion BCAA and associated antagonists （BCH, fluoxetine） can improve POFS by reducing the absorption of TRP that results in decreased synthesis of central 5-HT.