title: Impaired mastication reduced newly generated neurons at the accessory olfactory bulb and pheromonal responses in mice.
abstract: OBJECTIVE
  A large number of neurons are generated at the subventricular zone (SVZ) even during adulthood. In a previous study, we have shown that a reduced mastication impairs both neurogenesis in the SVZ and olfactory functions. Pheromonal signals, which are received by the vomeronasal organ, provide information about reproductive and social states. Vomeronasal sensory neurons project to the accessory olfactory bulb (AOB) located on the dorso-caudal surface of the main olfactory bulb. Newly generated neurons at the SVZ migrate to the AOB and differentiate into granule cells and periglomerular cells. This study aimed to explore the effects of changes in mastication on newly generated neurons and pheromonal responses.
  
  
  METHODS
  Bromodeoxyuridine-immunoreactive (BrdU-ir; a marker of DNA synthesis) and Fos-ir (a marker of neurons excited) structures in sagittal sections of the AOB after exposure to urinary odours were compared between the mice fed soft and hard diets.
  
  
  RESULTS
  The density of BrdU-ir cells in the AOB in the soft-diet-fed mice after 1 month was essentially similar to that of the hard-diet-fed mice, while that was lower in the soft-diet-fed mice for 3 or 6 months than in the hard-diet-fed mice. The density of Fos-ir cells in the soft-diet-fed mice after 2 months was essentially similar to that in the hard-diet-fed mice, while that was lower in the soft-diet-fed mice for 4 months than in the hard-diet-fed mice.
  
  
  CONCLUSIONS
  The present results suggest that impaired mastication reduces newly generated neurons at the AOB, which in turn impairs olfactory function at the AOB.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Asahikawa Medical University, Asahikawa 078-8510, Japan; Department of Sensory Physiology, Asahikawa Medical University, Asahikawa 078-8510, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Utsugi
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa 078-8510, Japan.
authors.forename: Sadaharu
authors.initials: S
authors.lastname: Miyazono
authors.affiliation: Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Tohbetu 061-0293, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Osada
authors.affiliation: Department of Oral and Maxillofacial Surgery, Asahikawa Medical University, Asahikawa 078-8510, Japan.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Matsuda
authors.affiliation: Department of Sensory Physiology, Asahikawa Medical University, Asahikawa 078-8510, Japan. Electronic address: yanagi@asahikawa-med.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kashiwayanagi
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine; D004032:Diet; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D008409:Mastication / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D055495:Neurogenesis / Q000502:physiology*; D009830:Olfactory Bulb / Q000166:cytology* / Q000502:physiology; D010675:Pheromones / Q000652:urine; D016760:Proto-Oncogene Proteins c-fos; D012903:Smell / Q000502:physiology*; D013997:Time Factors
chemical_list: D010675:Pheromones; D016760:Proto-Oncogene Proteins c-fos; D001973:Bromodeoxyuridine
keywords: Hard diet; Mastication; Olfactory function; Pheromone; Soft diet