title: Occlusal disharmony attenuates glucocorticoid negative feedback in aged SAMP8 mice.
abstract: To evaluate the mechanism underlying impaired cognitive function due to occlusal disharmony, we examined the effect of the bite-raised condition on spatial performance and hippocampal expression of glucocorticoid receptors (GR) and glucocorticoid receptor messenger ribonucleic acid (GRmRNA) using behavioral, immunohistochemical, and in situ hybridization techniques. Learning ability in the water maze test was significantly impaired in aged bite-raised mice compared with age-matched control mice. There was no difference between control and bite-raised young and middle-aged mice. Also, immunohistochemical and in situ hybridization analysis showed that the bite-raised condition enhanced the age-related decrease in GR and GRmRNA expression in the hippocampus. In particular, GR and GRmRNA expressions were significantly decreased in aged bite-raised mice compared to age-matched control mice. These findings suggest that the bite-raised condition in aged SAMP8 mice decreases GR and GRmRNA, which impairs the hypothalamic-pituitary-adrenal feedback inhibition, thereby leading to memory deficits.
authors.affiliation: Department of Pediatric Dentistry, Asahi University School of Dentistry, Mizuho, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Ichihashi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Arakawa
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Iinuma
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tamura
authors.forename: Kin-Ya
authors.initials: KY
authors.lastname: Kubo
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Iwaku
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sato
authors.forename: Minoru
authors.initials: M
authors.lastname: Onozuka
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D025461:Feedback, Physiological / Q000502:physiology; D005938:Glucocorticoids / Q000378:metabolism*; D006624:Hippocampus / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D008310:Malocclusion / Q000378:metabolism* / Q000503:physiopathology*; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid