Impairment of spatial memory and changes in astroglial responsiveness following loss of molar teeth in aged SAMP8 mice

Onozuka, Minoru; Watanabe, Kazuko; Nagasaki, Sachio; Jiang, Yi-Fan; Ozono, Satoru; Nishiyama, Kozaburo; Kawase, Toshio; Karasawa, Nobuyuki; Nagatsu, Ikuko

doi:10.1016/s0166-4328(99)00145-x

Cited by 91 publications

(124 citation statements)

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“…An in vivo study reported that aged molarless mice (removal of their upper molar teeth) showed impairment in the cholinergic system, spatial memory and degeneration of hippocampal neurons [8][9][10] . Thus, a recent relationship between the oral environment, which includes the task of chewing, and the brain, in particular the hippocampal regions that play an important role in learning and memory function, has been noted.…”

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confidence: 99%

Cell Proliferation in the Dentate Gyrus of Rat Hippocampus Is Inhibited by Soft Diet Feeding

et al. 2005

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Background: Recently it has become well accepted that neurogenesis occurs in the dentate gyrus of the hippocampus, a region important to memory and learning function in rodents and humans. Reports show that neurogenesis in the hippocampus is regulated by certain factors, such as exposure to an enriched environment, physical activity, aging and stress. The relationship between the change in the task of chewing as one oral environmental factor, and the mechanisms of hippocampal neuron generation are unclear. Objective: We examined whether cell proliferation varies by chewing tasks with different food textures in the dentate gyrus of the rat hippocampus. Methods: Wistar rats were divided into two groups, one was fed a solid diet, known as the hard-diet feeding group, and the soft-diet feeding group, which was fed a powder diet containing the same components as the solid one for 3, 7, 16 and 24 weeks. Thymidine analog 5-bromo-2′-deoxyuridine (BrdU) was used as a marker of cell proliferation within the dentate gyrus of the hippocampus and olfactory bulb. Results: The results of this study indicated that the total number of BrdU-positive cells in the hippocampal dentate gyrus significantly decreased with aging and were significantly fewer in the soft-diet feeding group than in hard-diet feeding group in 7-, 16- and 24-week-old rats after the BrdU injection. The change of BrdU-positive cell expression between soft and hard diets in 3- and 24-week-old rats was not observed in the olfactory bulb. Conclusion: It has been suggested that cell proliferation in the dentate gyrus of the rat hippocampus is characteristically suppressed by soft diet feeding.

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confidence: 99%

Cell Proliferation in the Dentate Gyrus of Rat Hippocampus Is Inhibited by Soft Diet Feeding

et al. 2005

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“…Based on these findings, we considered that our results are due to a decrease in peripheral 16) . Onozuka et al 17) reported that the number of pyramidal cells in the hippocampus CAI area in senile mice that had undergone maxillary molar grinding, extraction, or amputation of the masseteric nerve, decreased to 77% of the level in mice at the same age with normal molars, suggesting that decreases in the number of pyramidal cells was caused by functional masticatory insufficiency and resulted in cell death. Therefore, we consider that decreases in masticatory function in the senile period further facilitate nerve cell death in the hippocampus with aging, and this phenomenon might be due to changes in the suprachiasmatic nucleus.…”

Section: Discussionmentioning

confidence: 99%

“…Squire et al 19) reported that stress induces neuronal death in the hippocampus, and Onozuka et al 17) reported that increases in the corticosterone concentration are induced by maxillary molar grinding. Therefore, the functional masticatory insufficiency in these mice may be due to chronic stress.…”

Section: Discussionmentioning

confidence: 99%

Relationship between light and dark period activity cycles and oral condition in senescence-accelerated mice

Iinuma

Yasui

Oonishi

et al. 2011

Okajimas Folia Anat. Jpn.

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IntroductionThe aging of the Japanese society is associated with an increase in the number of patients with senile dementia, and provisions to deal with this problem are becoming increasingly important. There is a clear relationship between the oral condition and general health 1,2) , but the relationship between oral conditions with aging and dementia r emains unclear 3) . In the present study, we used s enescenceaccelerated mice (SAMP1) to evaluate the effects of tooth absence and masticatory abnormalities induced during the juvenile period on life cycle and activity at later ages during which peripheral symptoms of dementia appear. Rodents, however, are nocturnal animals with higher activity levels in the dark period than in the light period, showing an activity cycle that follows the biological clock, and diurnal activity levels in senile rats aged 90 to 108 weeks is significantly shorter than that in juvenile rats, with no differences in the activity levels between the light and dark periods. Further, spontaneous activity is decreased, indicating that the nocturnal behavior of senescent animals is disturbed 4) . In the present study, this characteristic was used as an index of dementia. Materials and MethodsFifty male SAMP1 mice were used. The strain was kindly donated by the Institute of Frontier Medical Sciences, Kyoto University. We bred brother-sister in the animal facility of the Central Research Division at the School of Dentistry, Asahi University. The SAMP8 mouse has an average life span of 12 months (about half life span of normal mice) and begins to show deficits in learning and memory and aging at 5 months. The characteristics of this strain were described in detail by Takeda et al. 5,6) . The a nimals were bred and maintained under conventional conditions; housed in groups of 5 in plastic cages (175 W × 245 D × 125 H mm) under temperature (23 ± 1°C), humidity (55 ± 2%), and light (12 h; light period, 6:00 -18:00; dark period, 18:00 -6:00) controlled conditions; and water was available ad libitum. This experiment was conducted Okajimas Folia Anat. Jpn., 88(1): 29-36, May, 2011 Relationship between light and dark period activity cycles and oral condition in senescence-accelerated mice Summary: We investigated the effect of tooth absence and masticatory abnormalities due to powdered food feeding starting during the juvenile period on light and dark period activity cycles in senescence-accelerated mice (SAMP1) . SAMP1 were divided into 5 groups: Group 1, maxillo-mandibular molar tooth extraction; Group 2, maxillary molar tooth extraction; Group 3, mandibular molar tooth extraction; Group 4, powdered food; and Group 5, sham-operated control. Senescence was observed earliest in the powdered food group. Total 24-hour activity was higher in the control group than in the four other groups. In the powdered food group, the dark period activity decreased to less than 60% of the total activity in the 36th week. In the tooth extraction groups (Groups 1-3), dark period activity decreased to less than 60% of...

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“…Recent studies suggest that deterioration of the oral environment causes various effects on the central nervous system, such as a decrease of spine numbers in the hippocampal CA1 area , an increase of plasma corticosterone (Yoshihara et al 2001), and transient activation of microglia (Kojo et al 2010). Furthermore, masticatory disorders reduce input activities in the hippocampus, thereby leading to deficits in learning and memory in aged senescence-accelerated prone 8 mice (Onozuka et al 1999(Onozuka et al , 2000Kubo et al 2005). In this report, we investigated the effects of increasing the occlusal vertical dimension on the mouse amygdaloid and hippocampal dynorphinergic nervous system using immunohistochemical, biochemical and behavioral techniques.…”

Section: Introductionmentioning

confidence: 99%

Occlusal Disharmony Transiently Impairs Learning and Memory in the Mouse by Increasing Dynorphin A Levels in the Amygdala

Yamada

Ono

Kubo

et al. 2013

Tohoku J. Exp. Med.

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Occlusal disharmony sometimes causes not only stiffness of neck but also psychiatric depression, suggesting that the condition of oral cavity may affect the central nervous system. Dynorphin A is an endogenous opioid peptide that specifically binds the κ-opioid receptor and has a protective role against stress. Dynorphinergic nervous system is intensely distributed in the amygdala and hippocampus that are coping areas with stress. As a model of malocclusion, we placed dental resin on the molars to increase the occlusal vertical dimension (bite-raise). After various survival times, we analyzed the amygdala and hippocampus by immunohistochemistry and immunosorbent assay (ELISA). Furthermore, the effects on learning and memory were assessed by Morris water maze test. In the amygdala, the levels of dynorphin A were increased on the 1st day after increasing the vertical dimension as indicated by immunohistochemical and ELISA assessments. The levels of dynorphin A returned to control levels on the 5th day. In the hippocampus, there were no noticeable changes in dynorphin A levels. The water maze test indicated that increasing the vertical dimension caused longer escape latency times on the 3rd day compared to those of sham-operated group. However, the bite-raised mice treated with a dynorphin antagonist, nor-binaltorphimine, showed similar escape latency times to the times of sham-operated group, even on the 3rd day. These results suggest that occlusal disharmony causes stress resulting in a transient increase of dynorphin A levels at least in the amygdala and that the increased dynorphin A levels transiently impair learning and memory.

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Impairment of spatial memory and changes in astroglial responsiveness following loss of molar teeth in aged SAMP8 mice

Cited by 91 publications

References 45 publications

Cell Proliferation in the Dentate Gyrus of Rat Hippocampus Is Inhibited by Soft Diet Feeding

Cell Proliferation in the Dentate Gyrus of Rat Hippocampus Is Inhibited by Soft Diet Feeding

Relationship between light and dark period activity cycles and oral condition in senescence-accelerated mice

Occlusal Disharmony Transiently Impairs Learning and Memory in the Mouse by Increasing Dynorphin A Levels in the Amygdala

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