慢性应激抑郁状态对大鼠外周神经内分泌因子生物节律的影响

目的：探讨慢性不可预见性应激状态下大鼠外周神经内分泌因子昼夜节律的表达特点。方法：成年雄性SD大鼠60只，随机分为模型组和对照组（n=30），采用束缚、摇晃、鼠笼倾斜、湿垫料、冷刺激、拥挤（整夜）、断食或断水、夹尾、昼/夜颠倒等慢性不可预知性温和刺激结合孤养方式，每天暴露于2种应激原中饲养21 d，建立抑郁症模型。测定应激前后大鼠糖水偏爱、旷场行为及高架十字迷宫行为学变化。连续24 h分6个时间点（ZT1、ZT5、ZT9、ZT13、ZT17、ZT21）处死动物取血，每个时间点处死5只大鼠。放免法测定6个时间点血清促肾上腺皮质激素（ACTH）含量，ELISA法测定6个相同时间点血浆皮质酮（CORT）、褪黑素（MT）、血管活性肠肽（VIP）含量，采用单一余弦法比较2组大鼠上述各指标的节律周期、振幅、峰值相位、中值的变化特点。结果：与对照组相比，模型大鼠体重增加值明显降低（P<0.01），各项行为学评分均显著减少（P<0.01）。慢性应激至抑郁样行为充分表达后，血浆ACTH、CORT的相位完全相反，时相大幅度提前，含量波动幅度减小，昼夜分泌节律紊乱；MT的24 h分泌节律完全丧失且整体水平下降，表达量显著降低；VIP虽仍存在24 h节律，但振幅明显降低，峰相位也延迟6 h，且表达量显著提高。结论：慢性应激抑郁状态可导致大鼠外周神经内分泌激素的近日节律非同步于SCN，表现为昼夜节律性和激素分泌量的异常。

Effects of chronic stress depression on the circadian rhythm of peripheral neuroendocrine hormone of rats

Objective: To investigate the circadian rhythmic alterations of plasma hormone and peptide induced by chronic unpredictable mild stress(CUMS).Methods: Sixty male SD rats were randomly divided into two groups, model group and control group(n=30). Rats in model group received CUMS procedure (restraint, rotation, cage tilt, wet sawdust, cold, crowding, food or water deprivation, clamp tail and reverse light/dark cycle). Rats were randomly exposed to two stressors every day for 3 weeks. Exploratory locomotor activity was assessed by open field test and anxiety-like behavior was measured by elevated plus-maze test, and lack of pleasure by sucrose preference test. Blood samples were collected at each of six time points zeitgeber time (ZT1, 5, 9, 13, 17 and 21), 5 rats were executed at each time point. Plasma concentrations of corticosterone(CORT), melatonin (MT) and vasoactive intestinal peptide (VIP) were detected by ELISA kits, and plasma concentration of adrenocorticotropic hormone (ACTH) was determined by radioimmunoassay. The circadian rhythm changes of serum CORT, MT, VIP and ACTH in each group were compared by using cosinor.Results: Compared with control group, locomotor activity, rearing, weight gain and sucrose consumption in model group were decreased significantly. The values of the percentage of open-arm time (OT) and open arm entries (OE) were obviously lower in the model group than those in the control group. The circadian rhythm of plasma ACTH and CORT showed an obvious disorder, including phase advance and decrease in amplitude, and markedly blunted circadian rhythm. There also showed a markedly blunted circadian rhythm and decreased levels of plasma MT. VIP still had 24-hour rhythm, but the amplitude was significantly lower, peak phase also delayed for six hours, and expression was significantly higher.Conclusion: CUMS induces these peptides and hormones desynchronized from suprachiasmatic nucleus(SCN), manifested as the disturbed circadian rhythms and the abnormal hormone secretion of these synchronizers.