Neural Substrates of Cognitive Decline in Aging Monkeys

描述（由申请人提供）：恒河猴是正常人类衰老的模型，能够在认知测试之后最佳保存脑组织用于多学科研究。拟议的研究将检验这一假设，即年龄相关的认知能力下降是由一系列轻度退行性变化引起的，这些变化始于中年早期，伴随白色物质的炎症和损伤，导致轴突的功能变化，并进展为神经元的功能和结构变化。我们将研究三组猴子，以测试这一假设的各个方面。第一个队列的36只猴将用于横断面研究，由涵盖5至30岁成年寿命的受试者组成。在行为测试后，MRI扫描将随后进行体内神经生理学和新的两阶段灌注固定，以提供新鲜和固定的组织，以识别认知下降背后的大脑变化。第二个队列的6只中年猴将按照队列1进行处理，不同之处在于它们将用混合醛进行灌注固定，用于电子显微镜检查，以补充现有样品，并允许鉴定超微结构变化，这些变化是中年出现的与认知下降相关的第一个变化。第三组12只中年早期猴（年龄13-15岁）将纵向随访4年以上，进行重复行为测试、脑部MRI扫描以及血液和CSF样本。由于认知障碍的患病率在13-15岁时较低，但在20岁时较高，因此行为数据将确定个体猴子的认知特征和下降速度。纵向MRI将揭示体内脑结构的同时变化，并且CSF和血液样本将允许跟踪生物标志物。对于队列1和3，灌注固定之前将进行复合动作电位的体内神经生理学评估。然后进行两阶段灌注，以便在固定大脑的其余部分之前立即从一个半球收集未固定的样本。新鲜组织将用于突触电流和动作电位的体外神经生理学、单细胞PCR以及潜在机制的生化和分子研究。固定的组织将用于解剖学研究，包括神经元数量的体视学研究和炎症及其他退行性过程的免疫细胞化学研究。

DESCRIPTION (provided by applicant): The rhesus monkey is a model of normal human aging that enables cognitive testing to be followed by optimal preservation of brain tissue for multidisciplinary studies. The proposed studies will test the hypothesis that age-related cognitive decline results from a cascade of mild degenerative changes beginning in early middle age with inflammation and damage in white matter that leads to functional changes in axons and progresses to functional and structural changes in neurons. We will study three cohorts of monkeys to test various aspects of this hypothesis. The first cohort of 36 monkeys will be used in a cross-sectional study and consist of subjects covering the adult life span from 5 to 30 years old. After behavioral testing, MRI scans will be followed by in vivo neurophysiology and a new two stage perfusion fixation to provide fresh and fixed tissue to identify brain changes underlying cognitive decline. A second cohort of 6 middle aged monkeys will be treated like cohort 1 except they will be perfusion fixed with mixed aldehydes for electron microscopy to supplement existing samples and allow identification of the ultrastructural changes that are the first changes to appear in middle age in association with cognitive decline. A third cohort of 12 early middle aged monkeys (ages 13-15) will be followed longitudinally for 4+ years with repeated behavioral testing, MRI scans of the brain, and samples of blood and CSF. As the prevalence of cognitive impairment is low at 13-15 but high by 20, behavioral data will identify the cognitive profile and rate of decline of individual monkeys. Longitudinal MRIs will reveal concurrent changes in the in vivo brain structure, and CSF and blood samples will allow biomarkers to be followed. For cohorts 1 and 3, perfusion fixation will be preceded by in vivo neurophysiological assessment of compound action potentials. Then the two stage perfusion will follow to allow immediate collection of unfixed samples from one hemisphere before the remainder of the brain is fixed. Fresh tissue will be used for in vitro neurophysiology of synaptic currents and action potentials, for single cell PCR, and for biochemical and molecular studies of underlying mechanisms. Fixed tissue will be used for anatomical studies, including stereological studies of neuron numbers and immunocytochemical studies of inflammation and other degenerative processes.