Influence of a long-term powdered diet on the social interaction test and dopaminergic systems in mice |
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Authors: | Fukie Niijima-Yaoita Masahiro Tsuchiya Hiroko Saito Yuka Nagasawa Shigeo Murai Yuichiro Arai Osamu Nakagawasai Wataru Nemoto Takeshi Tadano Koichi Tan-No |
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Affiliation: | 1. Department of Pharmacology, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan;2. Department of Aging and Geriatric Dentistry, Graduate School of Dentistry, Tohoku University, Seiryo-machi 2-1, Aoba-ku, Sendai 980-8575, Japan;3. Laboratory of Pharmacology, Faculty of Pharmaceutical Science, Aomori University, 2-3-1 Koubata, Aomori 030-0943, Japan;4. Department of Judotherapy, Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, 2-9-1 Ariake, Koto-ku, Tokyo 135-0063, Japan;5. Department of Environmental Health Science, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan |
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Abstract: | It is well known that the characteristics of mastication are important for the maintenance of our physical well-being. In this study, to assess the importance of the effects of food hardness during mastication, we investigated whether a long-term powdered diet might cause changes in emotional behavior tests, including spontaneous locomotor activity and social interaction (SI) tests, and the dopaminergic system of the frontal cortex and hippocampus in mice. Mice fed a powdered diet for 17 weeks from weaning were compared with mice fed a standard diet (control). The dopamine turnover and expression of dopamine receptors mRNA in the frontal cortex were also evaluated. Spontaneous locomotor activity, SI time and dopamine turnover of the frontal cortex were increased in powdered diet-fed mice. On the other hand, the expression of dopamine-4 (D4) receptors mRNA in the frontal cortex was decreased in powdered diet-fed mice. Moreover, we examined the effect of PD168077, a selective D4 agonist, on the increased SI time in powdered diet-fed mice. Treatment with PD168077 decreased the SI time. These results suggest that the masticatory dysfunction induced by long-term powdered diet feeding may cause the increased SI time and the changes in the dopaminergic system, especially dopamine D4 receptor subtype in the frontal cortex. |
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Keywords: | Powdered diet Mastication Social interaction test Frontal cortex Dopamine Locomotor activity |
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