The Gansu Zokor (myospalax Cansus) Circadian Rhythm Regulation Research

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.