AGE-RELATED CHANGES IN MONKEY CORTICAL PYRAMIDAL CELLS

描述(由申请人提供)：工作记忆是抽象思维、解决问题和认知灵活性等能力所必需的，在很大比例的人类和非人类灵长类动物中，随着正常年龄的增长，工作记忆显著受损。虽然已知这些能力在很大程度上是由前额叶皮质(PFC)的锥体细胞介导的，但PFC功能随年龄增长而下降的特定神经底物尚不清楚。鉴于我们的人口老龄化，这是一个高度相关的问题，拟议的研究将以创新的方式直接解决这个问题，该研究采用了一个独特的实验模型-恒河猴的行为特征。工作记忆任务期间的信息由PFC中第三层锥体细胞的动作电位(AP)放电速率以时间动态和特定的方式编码。初步研究表明，这些细胞在体外的放电频率与年龄有关，而且它们的放电频率与认知能力显著相关。这项建议的总体目标是在单个第3层锥体细胞内，全面和同时检查与年龄相关的细胞属性(离子电流、突触反应、形态)的相关变化，这些变化可能导致放电频率的功能显著变化。老年和幼年恒河猴将接受一系列认知任务的评估，从而能够确定认知损害的程度。从这些猴子制备的PFC切片中，全细胞膜片钳记录和第三层锥体细胞的荧光黄(LY)填充将被用于三个高度集成的特定目标。在目标1中，将使用电流钳记录来评估固有膜和AP的放电特性；随后，将使用电压钳分析影响AP放电的时间模式的电流(Lc、IAHP、sIAHP和Lh)，以检验这些电流的特性随年龄的变化导致放电频率增加的具体假设。在目标2中，电压钳记录将评估这些细胞中与年龄相关的谷氨酸和GABA能突触后电流的变化，以检验突触传递的变化与信号变化有关的特定假设。目的3实验将探索LY填充的第3层锥体细胞的详细树突构筑和树突棘随年龄的变化，以检验形态结构变化是这些细胞信号特性变化的基础这一特定假设。来自每个目标的数据将被交叉关联，并与老年猴子群体中的认知表现分数相关联。这种多方面的方法将提供关于正常衰老对单个神经元中各种但相互关联的细胞特性的影响的独特信息，这些特性在工作记忆任务的执行中起着关键作用。这些信息对于详细了解认知衰退的细胞机制是至关重要的，也是未来治疗干预措施发展的先决条件。

DESCRIPTION (provided by applicant): Working memory, which is essential for abilities such as abstract thinking, problem solving, and cognitive flexibility, is significantly impaired with normal aging in a large proportion of humans and non-human primates. While it is known that these abilities are mediated in large part by pyramidal cells of the prefrontal cortex (PFC), the specific neural substrates of age-related decline in PFC function are not known. Given our aging population, this is a highly relevant question that will be directly addressed in an innovative manner by the proposed studies, which employ a unique experimental model- the behaviorally characterized rhesus monkey. Information during working memory tasks is encoded in a temporally dynamic and specific manner by the action potential (AP) firing rates of layer 3 pyramidal cells in the PFC. Preliminary studies demonstrate that there is a significant age-related increase in the firing rates of these cells in vitro, and their firing rates are significantly associated with cognitive performance. The overall goal of this proposal is to comprehensively and simultaneously examine, within individual layer 3 pyramidal cells, age-related alterations in interrelated cellular properties (ionic currents, synaptic responses, morphology), which likely contribute to functionally significant alterations in firing rate. Aged and young rhesus monkeys will be assessed on a battery of cognitive tasks, enabling determination of degree of cognitive impairment. Whole-cell patch-clamp recordings and Lucifer Yellow (LY) filling of layer 3 pyramidal cells in PFC slices prepared from these monkeys will then be employed in three highly integrated Specific Aims. In Aim 1, intrinsic membrane and AP firing properties will be assessed with current-clamp recordings; subsequently, voltage-clamp analyses of currents that influence the temporal pattern of AP firing, (lc, IAHP, sIAHP and lh), will be used to test the specific hypothesis that age-related changes in the properties of these currents lead to increased firing rates. In Aim 2, voltage-clamp recordings will assess age-related changes in glutamatergic and GABAergic postsynaptic currents in these cells, testing the specific hypothesis that changes in synaptic transmission are related to altered signaling. Aim 3 experiments will explore age-related changes in the detailed dendritic architecture and dendritic spines of LY-filled layer 3 pyramidal cells, testing the specific hypothesis that alterations in morphological structure underlie changes in the signaling properties of these cells. Data from each of these aims will be cross correlated and also correlated with cognitive performance scores within the aged group of monkeys. This multi-faceted approach will provide unique information on the effects of normal aging on diverse but interrelated cellular properties within individual neurons that play a critical role in the execution of working memory tasks. Such information is vital to the development of a detailed understanding of the cellular mechanisms of cognitive decline, and a prerequisite for the future development of therapeutic interventions.