title: Attenuated hippocampus-dependent learning and memory decline in transgenic TgAPPswe Fischer-344 rats.
abstract: Alzheimer's disease (AD) is characterized by increased beta amyloid (Abeta) levels, extracellular Abeta deposits in senile plaques, neurofibrillary tangles, and neuronal loss. However, the physiological role of normal levels of Abeta and its parent protein, the amyloid precursor protein (APP) are unknown. Here we report that low-level transgenic (Tg) expression of the Swedish APP mutant gene (APPswe) in Fischer-344 rats results in attenuated age-dependent cognitive performance decline in 2 hippocampus-dependent learning and memory tasks compared with age-matched nontransgenic Fischer-344 controls. TgAPPswe rats exhibit mild increases in brain APP mRNA (56.8%), Abeta-42 (21%), and Abeta-40 (6.1%) peptide levels at 12 mo of age, with no extracellular Abeta deposits or senile plaques at 6, 12, and 18 mo of age, whereas 3- to 6-fold increases in Abeta levels are detected in plaque-positive human AD patients and transgenic mouse models. The data support the hypothesis that a threshold paradigm underlies Abeta-related pathology, below which APP expression may play a physiological role in specific hippocampus-dependent tasks, most likely related to its neurotrophic role.
authors.affiliation: Section of Molecular Medicine, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Nelson
authors.initials: N
authors.lastname: Ruiz-Opazo
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kosik
authors.forename: Lyle V
authors.initials: LV
authors.lastname: Lopez
authors.forename: Pia
authors.initials: P
authors.lastname: Bagamasbad
authors.forename: Lorenz Rb
authors.initials: LR
authors.lastname: Ponce
authors.forename: Victoria Lm
authors.initials: VL
authors.lastname: Herrera
mesh_terms: D000375:Aging; D000544:Alzheimer Disease / Q000209:etiology / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000032:analysis / Q000096:biosynthesis*; D016564:Amyloid beta-Protein Precursor / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D030801:Animals, Genetically Modified; D001921:Brain / Q000378:metabolism / Q000503:physiopathology; D003071:Cognition / Q000502:physiology*; D005518:Food Preferences / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D009154:Mutation; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D013037:Spatial Behavior / Q000502:physiology
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D012333:RNA, Messenger