色氨酸羟化酶2基因敲除对雄性大鼠行为的影响

Effects of tryptophan hydroxylase 2 gene knockout on male rat behavior

【目的】探究色氨酸羟化酶2(Tph2)基因敲除对雄性大鼠焦虑、抑郁样行为和社交行为的影响,为进一步研究五羟色胺(5-HT)系统对大鼠生长发育及行为的调控机制提供参考。【方法】以SD背景的雄性大鼠为研究对象,采用高效液相色谱串联高分辨质谱检测成年野生型大鼠(WT)和Tph2基因敲除(第6外显子(98 bp)及其前128 bp序列被敲除)大鼠(Tph2^(KO))脑内中缝核5-HT含量;比较10周龄WT和Tph2^(KO)大鼠的体质量;统计旷场试验范式中WT和Tph2^(KO)大鼠进入中心区域的时间、次数,以及高架十字迷宫范式中WT和Tph2^(KO)大鼠进入开放臂和闭合臂的时间、次数,从而判断大鼠的焦虑水平;统计强迫游泳范式中WT和Tph2^(KO)大鼠静止漂浮的时间,评估大鼠的抑郁样行为;统计三室试验范式中WT和Tph2^(KO)大鼠探索陌生同龄同性别大鼠的时间及探索空室的时间,评估大鼠的基础社交水平;统计社交新奇测试范式中WT和Tph2^(KO)大鼠探索陌生大鼠的时间,评估大鼠的社交新奇认知能力。【结果】Tph2^(KO)大鼠大脑中缝核5-HT含量为19.08 nmoL/g,极显著低于WT大鼠大脑中缝核5-HT含量(2075.00 nmol/g)(P<0.01)。10周龄Tph2^(KO)大鼠体质量为235.90 g/只,极显著低于WT大鼠的体质量(317.90 g/只)(P<0.01)。旷场试验中Tph2^(KO)大鼠探索中心区域的时间为30.00 s,次数为6.50次,与WT大鼠(38.76 s,9.90次)无显著差异(P>0.05)。高架十字迷宫试验中Tph2^(KO)大鼠探索开放臂的时间为69.89 s,次数为5.40次,与WT大鼠(66.25 s,4.30次)无显著差异(P>0.05)。强迫游泳试验中Tph2^(KO)大鼠静止漂浮的时间(43.92 s)与WT大鼠(27.79 s)无显著差异(P>0.05)。社会互动试验中Tph2^(KO)大鼠社会互动时间为224.00 s,极显著高于探索空室的时间(12.57 s)(P<0.01);WT大鼠社交互动时间为258.00 s,极显著高于探索空室的时间(26.34 s)(P<0.01)。社交新奇认知试验中Tph2^(KO)大鼠探索陌生鼠2的时间为73.92 s,与探索陌生鼠1的时间(59.71 s)无显著差异(P>0.05);WT大鼠探索陌生鼠2的时间为124.00 s,极显著高于探索陌生鼠1的时间(69.88 s)(P<0.01)。【结论】Tph2基因敲除导致雄性大鼠大脑中缝核5-HT含量显著降低,体质量和社交新奇认知能力均显著降低。

【Objective】The effects of tryptophan hydroxylase 2(Tph2)knockout on levels of anxiety and depression as well as social preference of male rats were detected to provide basis for further research on regulatory mechanisms of 5-HT system on growth,development and behavior of rats.【Method】The 5-HT levels in brain of wild-type rats(WT)and Tph2 knockout(Exon 6(98 bp)and its preceding 128 bp sequence were knocked out)rats(Tph2^(KO))were measured by high performance liquid chromatography tandem high resolution mass spectrometry.The weights of 10-week-old WT and Tph2^(KO) rats were measured.Through the elevated plus-maze test(EPM)and open field test(OFT),entries and time in the open arm in the EPM and in the center zone in the OFT were calculated to assess anxiety levels.The forced swimming test was performed to evaluate the depression-like behavior by calculating the immobility time of rats.Sociability and social novelty were evaluated using the three-chamber test.Total interaction times with strangers were measured in different trials.【Result】The level of 5-HT in raphe nucleus in Tph2^(KO) rats(19.08 nmoL/g)was significantly lower than that in WT rats(2075.00 nmol/g)(P<0.01).The weight of Tph2^(KO) rats(235.90 g)was significantly lower than WT rats(317.90 g)(P<0.01).There was no significant difference in the time of exploring central zone between Tph2^(KO) rats(30.00 s)and WT rats(38.76 s)in the OFT(P>0.05).There was no significant difference in entries of exploring central zone between Tph2^(KO) rats(6.50)and WT rats(9.90)in the OFT(P>0.05).There was no significant difference in the time of exploring open arm between Tph2^(KO) rats(69.89 s)and WT rats(66.25s)in the EPM(P>0.05).There was no significant difference in entries of exploring open arm between Tph2^(KO) rats(5.40)and WT rats(4.30)in the EPM(P>0.05).There was no significant difference in the immobility time between Tph2^(KO) rats(43.92 s)and WT rats(27.79 s)in the forced swimming test(P>0.05).In the social interaction test,the total social time(224.00 s)was significantly higher than the time of exploring empty chamber(12.57 s)in Tph2^(KO) rats(P<0.01),and the total social time(258.00 s)was significantly higher than the time of exploring empty chamber(26.34 s)in WT rats(P<0.01).In the social novelty test,the time of exploring stranger 2(73.92 s)was not significantly different from the time of exploring stranger 1(59.71 s)in Tph2^(KO) rats(P>0.05),and the time of exploring stranger 2(124.00 s)was significantly higher than the time of exploring stranger 1(69.88 s)in WT rats(P<0.01).【Conclusion】The weight and social novelty recognition of male rats decreased significantly with the loss of 5-HT in raphe nucleus.