title: Influence of a long-term powdered diet on the social interaction test and dopaminergic systems in mice.
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.
authors.affiliation: Department of Pharmacology, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan. niijima@tohoku-pharm.ac.jp
authors.forename: Fukie
authors.initials: F
authors.lastname: Niijima-Yaoita
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Hiroko
authors.initials: H
authors.lastname: Saito
authors.forename: Yuka
authors.initials: Y
authors.lastname: Nagasawa
authors.forename: Shigeo
authors.initials: S
authors.lastname: Murai
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Arai
authors.forename: Osamu
authors.initials: O
authors.lastname: Nakagawasai
authors.forename: Wataru
authors.initials: W
authors.lastname: Nemoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tadano
authors.forename: Koichi
authors.initials: K
authors.lastname: Tan-No
mesh_terms: D000821:Animal Feed; D000818:Animals; D001483:Base Sequence; D001549:Benzamides / Q000494:pharmacology; D017931:DNA Primers; D004032:Diet; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism; D007398:Interpersonal Relations; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010879:Piperazines / Q000494:pharmacology; D011208:Powders; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D011954:Receptors, Dopamine / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: D001549:Benzamides; D017931:DNA Primers; D018491:Dopamine Agonists; C477501:N-((4-(2-cyanophenyl)-1-piperazinyl)methyl)-3-methylbenzamide; D010879:Piperazines; D011208:Powders; D012333:RNA, Messenger; D011954:Receptors, Dopamine; D004298:Dopamine
keywords: Dopamine; Frontal cortex; Locomotor activity; Mastication; Powdered diet; Social interaction test