Project description:Background: Age-related cognitive deficits negatively affect quality of life and can presage serious neurodegenerative disorders. Despite sleep disruption’s well-recognized negative influence on cognition, and its prevalence with age, surprisingly few studies have tested sleep’s relationship to cognitive aging. Methodology: We measured sleep stages in young adult and aged F344 rats during inactive (enhanced sleep) and active (enhanced wake) periods. Animals were behaviorally characterized on the Morris water maze and gene expression profiles of their parietal cortices were taken. Principal Findings: Water maze performance was impaired, and inactive period deep sleep was decreased with age. However, increased deep sleep during the active period was most strongly correlated to maze performance. Transcriptional profiles were strongly associated with behavior and age, and were validated against prior studies. Bioinformatic analysis revealed increased translation and decreased myelin/ neuronal pathways. Conclusions: The F344 rat appears to serve as a reasonable model for some common sleep architecture and cognitive changes seen with age in humans, including the cognitively disrupting influence of active period deep sleep. Microarray analysis suggests that the processes engaged by this sleep are consistent with its function. Thus, active period deep sleep appears temporally misaligned but mechanistically intact, leading to the following: first, aged brain tissue appears capable of generating the slow waves necessary for deep sleep, albeit at a weaker intensity than in young. Second, this activity, presented during the active period, seems disruptive rather than beneficial to cognition. Third, this active period deep sleep may be a cognitively pathologic attempt to recover age-related loss of inactive period deep sleep. Finally, therapeutic strategies aimed at reducing active period deep sleep (e.g., by promoting active period wakefulness and/or inactive period deep sleep) may be highly relevant to cognitive function in the aging community. KEYWORDS: frontal cortex, rat, young or aged We implanted young and aged Fischer 344 rats (n = 6/ group) with wireless EEG, EMG and movement monitoring devices to measure sleep architecture. Animals were trained in the Morris water maze to assess cognitive function, and frontal cortices were removed for microarray analysis.sleep disruption and cognitive decline.

Project description:Background: Age-related cognitive deficits negatively affect quality of life and can presage serious neurodegenerative disorders. Despite sleep disruption’s well-recognized negative influence on cognition, and its prevalence with age, surprisingly few studies have tested sleep’s relationship to cognitive aging. Methodology: We measured sleep stages in young adult and aged F344 rats during inactive (enhanced sleep) and active (enhanced wake) periods. Animals were behaviorally characterized on the Morris water maze and gene expression profiles of their parietal cortices were taken. Principal Findings: Water maze performance was impaired, and inactive period deep sleep was decreased with age. However, increased deep sleep during the active period was most strongly correlated to maze performance. Transcriptional profiles were strongly associated with behavior and age, and were validated against prior studies. Bioinformatic analysis revealed increased translation and decreased myelin/ neuronal pathways. Conclusions: The F344 rat appears to serve as a reasonable model for some common sleep architecture and cognitive changes seen with age in humans, including the cognitively disrupting influence of active period deep sleep. Microarray analysis suggests that the processes engaged by this sleep are consistent with its function. Thus, active period deep sleep appears temporally misaligned but mechanistically intact, leading to the following: first, aged brain tissue appears capable of generating the slow waves necessary for deep sleep, albeit at a weaker intensity than in young. Second, this activity, presented during the active period, seems disruptive rather than beneficial to cognition. Third, this active period deep sleep may be a cognitively pathologic attempt to recover age-related loss of inactive period deep sleep. Finally, therapeutic strategies aimed at reducing active period deep sleep (e.g., by promoting active period wakefulness and/or inactive period deep sleep) may be highly relevant to cognitive function in the aging community. KEYWORDS: frontal cortex, rat, young or aged

Project description:The decline of cognitive function is a feature of normal human aging and is exacerbated in AlzheimerM-bM-^@M-^Ys disease (AD). DNA repair declines in brain cells during normal aging and even more so in AD. Here we show that experimental reduction in levels of the base excision repair enzyme, DNA polymerase M-NM-2 (Polb) renders neurons vulnerable to age-related dysfunction and degeneration in a mouse model of AD. Whereas 3xTgAD mice exhibit age-related extracellular amyloid b-peptide (Ab) accumulation and cognitive deficits, but no neuronal death, 3xTg/Polb+/- mice accumulates intracellular Ab and neurons die in the hippocampus and cerebral cortex. The DNA repair-deficient 3xTgAD mice exhibited increased DNA strand breaks and apoptotic caspase activation with loss of hippocampal volume, and impaired synaptic plasticity and memory retention. Molecular profiling revealed remarkable similarities in gene expression alterations in brain cells of AD patients and 3xTgAD/Polb+/- mice including multiple abnormalities suggestive of impaired cellular bioenergetics. Our findings demonstrate that a modest decrement in oxidative DNA damage processing is sufficient to render neurons vulnerable to AD-related pathogenic molecular and cellular alterations that result in the dysfunction and death of neurons, and associated cognitive deficits. 4 mouse strains were used in these experiments, the 3xTgAD and Pol M-NM-2 (+/-) mice were bred at the National Institute on Aging (Baltimore, Maryland). The original line 3xTgAD line was generated as described previously (Oddo, et. al 2003) and possess APPswe, PS1M146V, and tauP301L mutations. DNA polymerase beta heterozygous mice, Pol M-NM-2 (+/-), were crossed with the 3xTgAD mice to generate a 3xTgAD/Pol M-NM-2 (+/-) mouse. The Wt strain is C57Bl/6. At 20 months of age these mice were euthanized by cervical dislocation, the brain removed from the skull and dissected into regions of interest, the prefrontal cortex was used for the microarray studies.

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