海马5-羟色胺受体4及let-7a在双重应激诱发大鼠抑郁中的作用

目的研究双重应激对大鼠行为及其海马内5-羟色胺受体4（HTR4）及microRNAlet-7a水平的影响，探索海马内HTR4及let-7a的基因表达异常是否参与双重应激诱发抑郁的过程，及let-7a是否参与海马内HTR4基因表达的调控。方法将新生sD雄性大鼠，按窝别随机分为双重应激组（DS组，n=6）和正常对照组（C组，n=6）。DS组大鼠于出生后即接受两周母爱剥夺应激处理，至10周龄时再接受3周慢性不可预知性应激处理，C组大鼠不接受任何实验性处理；待大鼠13周龄时，采用旷场试验、强迫游泳及糖水偏爱实验评定两组大鼠的抑郁水平，并采用实时定量RT-PCR法检测大鼠海马内let-7a水平，采用WesternBlot法检测大鼠海马内HTR4的蛋白水平。结果与c组相比，Ds组大鼠在旷场试验中的直立次数较少分别为（19．00±5．73）次及（7．50±2．35）次]（P〈0．05），DS组大鼠在强迫游泳实验中的静止漂浮时间较长分别为（70．33±1．16）S及（110．17±1．72）s]（P〈0．05），DS组大鼠在糖水偏爱实验中的糖水偏爱率较低分别为0．80±0．73及0．52±0．26]（P〈0．05），DS组大鼠海马内HTR4蛋白水平降低分别为（1．44±0．38）及（0．46±0．29）]（P〈0．01），let-7a水平较高分别为（0．04±0．01）及（1．58±0．27）]（P〈0．01）；皮尔逊相关分析显示，大鼠糖水偏爱率与其海马内let-7a表达量呈负相关（r=-0．653，P〈0．05），与其海马内HTR4蛋白表达量呈正相关（r=0．774，P〈0．01），大鼠海马内let-7a与HTR4蛋白表达量呈负相关（r=-0．803，P〈0．01）。结论DS可诱发大鼠抑郁样表型，影响大鼠海马内HTR4及let-7a的基因表达；大鼠海马内HTR4及let-7a可能参与调节其快感体验能力；let-7a可能参与海马内HTR4基因表达的调控。

The dysregulation of hippocampal serotonin receptor 4 and let-7a were associated with dual stress-induced depression in rats

Objective To study the effect of dual stress on the behaviors and the expression of hippocam- pal let-7a and serotonin receptor 4（HTR4） in rats. Methods Newborn SD rats were randomly divided into dual stress group （DS, n= 6） and control group （C, n= 6）. The DS rats were deprived of the mother care 6 hours per day from postnatal day 1 to 14 and then were exposed to chronic mild stress for 21 days from 10 weeks old,while the rats from C group received no experimental handle but husbandry care.Open field test ,forced swimming test and sucrose consumption test were conducted to evaluate rats＇ depression-like behaviors at the age of thirteen weeks. The let-7a level in hippocampus was detected by real-time Polymerase Chain Reaction and the HTR4 protein level was measured by Western Blotting. Results In the open filed test, the rearing times of DS rats was shorter than that of C group（（7.50±2.35） vs （ 19.00±5.73）, P〈0.05） .In the forced swimming test,the floating time of DS rats was longer than that of C group （ （ 110.17± 1.72） s vs （ 70.33±1.16） s, P〈0.05 ）.In the sucrose consumption test, DS rats consumed less sucrose than rats from C group did（（0.80±0.73） vs （0.52±0.26） , P〈 0. 05 ） . The protein level of hippocampal HTR-4 in DS group was lower than that of C group （ （ 1.44 ± 0.38 ） vs （ 0.46 ± 0.29 ）, P〈 0.01 ）. The let-Ta level in DS group was higher than that of C group（ （ 0.04±0.01 ） vs （ 1.58±0.27）, P〈0.01 ） .The Pear- son correlation analysis revealed that the sucrose preference rate of rats were negatively and positively correlated with hippocampal let-7a and HTR4 level respectively（ r=-0.653, P〈0.05; r= 0.774, P〈0.01 ） , and hippocampal let-7a level showed negative association with HTR4 protein level （ r=-0.803, P〈0.01）. Conclusion Dual stress can induce the depressive behaviors of rats and affect the expression of let-7a and HTR4 in hippocampus. Hipp- oeampal HTR4 and let-7a might be involved in determining individual ability to experience pleasure in rats;and hippocampal let-7a may be involved in the regulation of HTR4 gene expression in rats.