甘肃鼢鼠（Myospalax cansus）昼夜节律调节研究

【作者】 孟衫衫；

【导师】 李金钢；

【作者基本信息】 陕西师范大学 ， 动物学， 2010， 硕士

【摘要】 节律性是生命的基本特征之一,昼夜节律是哺乳动物最常见的一种生物节律,是生物界的各种功能为了适应地球自转的昼夜环境周期性的变化而产生的。经过长期进化,生物机体内发育分化出一个特殊的结构一生物钟,用来协调各种不同组织和器官的昼夜节律。在哺乳动物中,控制昼夜节律的主要生物钟位于下丘脑视交叉上核,可节律性地释放多种神经肽,并将节律性信号传递给松果腺,使之有节律地合成与释放褪黑素。很多研究已经证明,光周期是影响生物钟基因表达进而调控生物节律的主要环境因子,它们对生物钟基因表达的调控机制存在着保守性和特异性。由于长期生活在地下黑暗环境中,地下鼠视觉系统已严重退化,但是有关感受光周期的“非成像”视觉通路结构却高度发达,仍然能够感光和感知外界光周期并产生与外界昼夜循环同步的生物节律现象。这意味着,地下鼠的视觉系统在退化过程中保留了有功能的生物钟系统对其自身有重要的意义。对地下鼠的昼夜节律以及与昼夜节律有关的视觉系统进行研究,不仅有助于阐明地下啮齿类视觉系统的功能、生物进化与环境的关系,同时为地下鼠的昼夜节律调节机制以及与节律行为有关的其它行为研究提供参考。甘肃鼢鼠是我国黄土高原地区特有的地下鼠种类,前期研究发现,甘肃鼢鼠能识别明暗环境,且能区分不同波长的光,在笼养条件下夏秋季节具有明显的行节律。但对其昼夜节律的调节尚未深入研究。本文对实验室饲养和人工控制光照条件下的甘肃鼢鼠,利用行为学分析和免疫组织化学方法相结合,对其昼夜节律调节功能做了探讨,得到结论如下：1.用行为学方法观察到在LD(L：6：00-18：00,D：18：00-6：00)光照模式下,甘肃鼢鼠表现出明显的夜间活动偏好,在24 h内行为节律出现两个高峰,并且能维持稳定,说明甘肃鼢鼠虽生活在地下黑暗洞道中,但其活动具有明显的昼夜节律。意味着能够感受光信号并且能调节自己活动与之相应。2.观察到在DL(L：18：00-6：00,D：6：00-18：00)光照模式下,甘肃鼢鼠能调节自己的活动节律与LD光周期保持一致。光照模式的改变引起行为活动节律的改变也证实了甘肃鼢鼠能识别明暗环境,并且证明甘肃鼢鼠具有有功能的生物钟,能对周期性光刺激做出反应。3.用免疫组化方法检测到甘肃鼢鼠下丘脑视交义上核褪黑素受体的表达具有明显节律性。在LD光照模式下峰谷出现在夜中期即24点,峰值出现在日中期即12点,与褪黑素含量水平夜间高白昼低相符合。意味着甘肃鼢鼠能辨识明暗周期。4.在DL光照模式下,褪黑素受体表达也具有明显节律性,表现出峰值出现在24点,即主观日中期12点。峰谷出现在12点,即主观夜中期24点。该节律与标准LD光照模式下致,说明甘肃鼢鼠能够调节其生物钟。5.由于甘肃鼢鼠是独居种类,排除了群居性社会因素对节律调节的因素,在实验室条件下,无降雨量和温度的影响,因此,光照周期是影响生物钟节律的重要因子。总之,对甘肃鼢鼠昼夜节律调节的研究结果表明,甘肃鼢鼠虽然眼睛已经极度退化,可能不具有将视觉信息转变成视觉图像的能力,但有关感受光周期的“非成像”视觉通路结构却依然存在,仍然具有感光和感知外界光周期并产生与外界昼夜循环同步的生物节律现象。甘肃鼢鼠具有有功能性的生物钟,可以在明暗周期中调节昼夜节律,意味着节律振荡器能够接收光信号,因而光是一种潜在的振荡因子。但是否是一种主要因子仍需考证。更多还原

【Abstract】 Rhythm is one of the basic characteristics of life. Circadian rhythm is the most common type of mammalian circadian rhythm.It is one biological function of the day and night in order to adapt to Earth’s rotation changes in the environment. After a long evolution, a special organ-the biological clock developed in the body to coordinate the circadian rhythm of a variety of tissues and organs. In mammals, the main biological clock controlling circadian rhythms is the hypothalamic suprachiasmatic nucleus, which can release a variety of neuropeptides, and transfer the signal to the pineal gland, so that synthesis and release melatonin rhythmicity. Many studies have shown that the photoperiod is the main environmental factors which affect the expression of circadian clock gene regulation.Their mechanism of circadian clock gene expression in the existence is conservative and specificity.As a result of living in the dark long time, the visual system of subterranean rodents has degraded seriously.But the "non-imaging" visual pathway structures that can feel light cycle are highly developed.It is still able to fell light cycle and produce day and night cycle synchronization with the outside biological rhythmicity. It suggested that the functional biological clock system may be important to the subterranean rodents. Studing the circadian rhythm and visual system of underground rodent will help to know more about the visual system functions and to further clarify the relationship between biological evolution and the environment,at the same time,provid for reference about regulatory mechanisms of the circadian rhythm of underground rats and behavior with the rhythm of the other acts. Myospalax cansus is an unique subterranean rodents in Loess Plateau.Preliminary laboratory study found that Myospalax cansus can identify light and dark and distinguish the different wavelengths of light.Their behavior in captive has obvious rhythm in summer and autumn. However, the regulation of its circadian rhythm has not been studied deeply. In this paper,we discussed the function of its circadian rhythm regulation who were reared under laboratory conditions in artificial control on light,by behavior analysis and immunohistochemistry combined.the conclusions are as follows:1.With the observed behavior in the LD(L:6:00～18:00, D:18:00～6:00) illumination mode, Myospalax cansus showed significant nocturnal preferences, appeared two behavior peaks in 24h rhythm and can maintain stability.It indicates that though Myospalax cansus living in the underground dark tunnel,its activities have significant circadian rhythm.It means that Myospalax cansus are able to feel the light signal and adjust their activities in the corresponding. 2.Observed behavior in the DL(L:18:00-6:00,D:6:00-18:00)illumination mode, Myospalax cansus can adjust their activity rhythm consistent with the LD photoperiod. Activity rhythm of behavior change with illumination model change also proves they are able to identify light and dark environments and have a functional biological clock to respond to the periodic light stimulation.3.There is obvious rhythm in expression of melatonin receptor in SCN detected by immunohistochemistry. In LD light mode the valley in the middle of the night and the peak appears in the mid-day consistent with the melatonin concentration levels who shows high in dark and low in the day. It means that light inhibits melatonin concentration in plasma.Myospalax cansus can identify light and dark cycle.4.1n the DL light mode, the expression of melatonin receptors also has obvious rhythm, showing peak in mid-night, or mid-subjective day,and valley in the mid day, or mid-subjective night.This rhythm consistent with standard mode LD light shows Myospalax cansus able to adjust their biological clock.5.As Myospalax cansus is the single lifestyle,social factors regulation circadian rhythm is unuseful.In laboratory conditions, no precipitation and temperature changes,thus,photoperiod is the important factor affecting biological clock rhythm.6. Myospalax cansus is seasonal breeding animal and there were significant differences in rhythm between summer season and autumn,suggesting the retention of functional circadian system is useful for its seasonal breeding activities.In conclusion,one all account results above show that although the eyes of Myospalax cansus has been extremely degraded and may not have the capacity of imaging,the feeling of light cycle and "non-imaging" visual pathway structures still have function,and have the phenomenon of biological rhythms that produce day and night cycle synchronization with the outside. Myospalax cansus have a functional clock so that can adjust circadian rhythm to the light and dark cycle.It means that oscillator can receive optical signals, and thus light is a potential shock factor.But it is still unkown if it is a major factor.更多还原