The effect of the chewing reduction on the cerebral functions of the mouse

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[Purpose] The present study was carried out to clarity whether the differences of chewing frequency affected the development of cerebral functions of the mouse.[Method] Mice were divided into three groups and each was feded by normal pellet diet (control), powdered diet or bulk diet for one month (short period) and four months (long period). As indexes forcerebral functions, mneme force and learning capability of the mouse were measured by three different maze apparatuses. Furthermore, after the end of the all behavioral testing, the levels of several central neurotransmitters and related metabolites were measured by HPLC-ECD methods in cerebral cortex and hippocampus.[Results] 1. The memory retrieval force of a short-term powdered group was less than the in a control group. This result suggests that the development of memory retrieval ability of the mouse already fixed in the brain is inferior.2. The learning ability of a short-term bulk diet group was superior to that ability of the control. This result suggests that laming ability of the mouse which is increased the chewing frequency is higher than the control.3. On the other hand, the memory retrieval force of a long-term powdered group did not differ from the control group. This result suggests that the difference of the memory retrieval ability of the mouse recognized in the growth period disappears after the maturation.4. The differences in tile chewing frequency did not influence the levels of the several central neurotransmitters and the related metabolic compounds.[Discussion] This study is not a result of extrapolating for the human, because it was done using the mouse. However, the present study suggest a possibility that the chewing frequency in the growth period is important for the functions development of the central nervous system. Further experiments may be needed in a future.