title: Tooth loss early in life suppresses neurogenesis and synaptophysin expression in the hippocampus and impairs learning in mice.
abstract: OBJECTIVE
  Tooth loss induced neurological alterations through activation of a stress hormone, corticosterone. Age-related hippocampal morphological and functional changes were accelerated by early tooth loss in senescence-accelerated mouse prone 8 (SAMP8). In order to explore the mechanism underlying the impaired hippocampal function resulting from early masticatory dysfunction due to tooth loss, we investigated the effects of early tooth loss on plasma corticosterone levels, learning ability, neurogenesis, and synaptophysin expression in the hippocampus later in life of SAMP8 mice.
  
  
  METHODS
  We examined the effects of tooth loss soon after tooth eruption (1 month of age) on plasma corticosterone levels, learning ability in the Morris water maze, newborn cell proliferation, survival and differentiation in the hippocampal dentate gyrus, and synaptophysin expression in the hippocampus of aged (8 months of age) SAMP8 mice.
  
  
  RESULTS
  Aged mice with early tooth loss exhibited increased plasma corticosterone levels, hippocampus-dependent learning deficits in the Morris water maze, decreased cell proliferation, and cell survival in the dentate gyrus, and suppressed synaptophysin expression in the hippocampus. Newborn cell differentiation in the hippocampal dentate gyrus, however, was not affected by early tooth loss.
  
  
  CONCLUSIONS
  These findings suggest that learning deficits in aged SAMP8 mice with tooth loss soon after tooth eruption are associated with suppressed neurogenesis and decreased synaptophysin expression resulting from increased plasma corticosterone levels, and that long-term tooth loss leads to impaired cognitive function in older age.
authors.affiliation: Seijoh University Graduate School of Health Care Studies, 2-172 Fukinodai, Tokai, Aichi, 476-8588, Japan. Electronic address: kubo@seijoh-u.ac.jp.
authors.forename: Kin-Ya
authors.initials: KY
authors.lastname: Kubo
authors.affiliation: Departments of Pediatric Dentistry, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu, 501-0296, Japan.
authors.forename: Chika
authors.initials: C
authors.lastname: Murabayashi
authors.affiliation: Departments of Pediatric Dentistry, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu, 501-0296, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Kotachi
authors.affiliation: Departments of Pediatric Dentistry, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu, 501-0296, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Departments of Prosthodontics, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu, 501-0296, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Mori
authors.affiliation: Department of Molecular Diagnostics, Kitasato University School of Allied Health Science, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 252-0373, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Judo Therapy and Medical Science, Faculty of Medical Science, Nippon Sport Science University, Yokohama 227-0033, Kanagawa, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Onozuka
authors.affiliation: Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, Fukuoka, 807-8555, Japan.
authors.forename: Kagaku
authors.initials: K
authors.lastname: Azuma
authors.affiliation: Departments of Pediatric Dentistry, Asahi University School of Dentistry, 1851-1 Hozumi, Mizuho, Gifu, 501-0296, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Iinuma
mesh_terms: D000367:Age Factors; D000818:Animals; D001835:Body Weight; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival; D003071:Cognition / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D018891:Dentate Gyrus / Q000166:cytology / Q000378:metabolism / Q000503:physiopathology; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism / Q000503:physiopathology*; D007150:Immunohistochemistry; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D051379:Mice; D055495:Neurogenesis / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology; D016708:Synaptophysin / Q000378:metabolism / Q000502:physiology*; D016388:Tooth Loss / Q000503:physiopathology*
chemical_list: D016708:Synaptophysin; D003345:Corticosterone
keywords: Cognitive function; Early tooth loss; Hippocampus; Neurogenesis; Synaptophysin