title: Chewing under restraint stress inhibits the stress-induced suppression of cell birth in the dentate gyrus of aged SAMP8 mice.
abstract: To investigate the mechanisms underlying impaired hippocampal function resulting from masticatory dysfunction, we examined the effects of the molarless condition on cell proliferation and the effect of the administration of metyrapone, which suppresses the stress-induced rise in plasma corticosterone levels, on cell proliferation in the hippocampal dentate gyrus (DG) of aged senescence-accelerated prone (SAMP8) mice. In addition, we examined whether chewing under restraint stress prevents the stress-induced suppression of cell proliferation. In aged mice, the molarless condition suppressed cell proliferation in the hippocampal DG. Vehicle-injected molarless mice had significantly higher plasma corticosterone levels than vehicle-injected control and metyrapone-injected molarless mice, in association with decreased cell proliferation in the hippocampal DG. Pretreatment with metyrapone inhibited the increase in plasma corticosterone levels induced by the bite-raised condition, and also attenuated the reduction in cell proliferation. Immobilization stress suppressed cell proliferation in the hippocampal DG, but chewing under restraint stress blocked the stress-induced suppression of cell proliferation in the DG. These results suggest that the morphologic deficits induced by the molarless condition in aged SAMP8 mice are a result of increased plasma corticosterone levels, and that chewing under restraint stress prevents the stress-induced suppression of cell birth in the DG.
authors.affiliation: Seijoh University Graduate School of Health Care Studies, 2-172 Fukinodai, Tokai, Aichi 476-8588, Japan. kubo@seijoh-u.ac.jp
authors.forename: Kin-ya
authors.initials: KY
authors.lastname: Kubo
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sasaguri
authors.forename: Yumie
authors.initials: Y
authors.lastname: Ono
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Toru
authors.initials: T
authors.lastname: Takahashi
authors.forename: Kazuko
authors.initials: K
authors.lastname: Watanabe
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Karasawa
authors.forename: Minoru
authors.initials: M
authors.lastname: Onozuka
mesh_terms: D000375:Aging / Q000473:pathology*; D000818:Animals; D049109:Cell Proliferation; D003345:Corticosterone / Q000097:blood; D018891:Dentate Gyrus / Q000473:pathology*; D008297:Male; D008409:Mastication; D008797:Metyrapone / Q000494:pharmacology; D051379:Mice; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000473:pathology* / Q000503:physiopathology
chemical_list: D003345:Corticosterone; D008797:Metyrapone