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，在大部分人类和非人类灵长类动物中随着正常衰老而显著受损。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，但与年龄相关的PFC功能下降的特定神经基质尚不清楚。考虑到我们的人口老龄化，这是一个高度相关的问题，将直接解决在一个创新的方式提出的研究，其中采用了一个独特的实验模型-行为特征的恒河猴。工作记忆任务中的信息是由PFC中第3层锥体细胞的动作电位（AP）放电率以时间动态和特定的方式编码的。初步研究表明，这些细胞的放电率在体外有一个显着的年龄相关的增加，其放电率与认知性能显着相关。本提案的总体目标是全面和同时检查，在个别层3锥体细胞，年龄相关的变化在相互关联的细胞特性（离子电流，突触反应，形态），这可能有助于在功能上显着的改变放电率。将对老年和幼龄恒河猴进行一系列认知任务评估，以确定认知障碍的程度。然后，将在三个高度整合的特定目标中采用全细胞膜片钳记录和从这些猴制备的PFC切片中第3层锥体细胞的荧光黄（LY）填充。在目标1中，将使用电流钳记录评估内在膜和AP放电特性;随后，将使用影响AP放电时间模式的电流（lc、IAHP、sIAHP和lh）的电压钳分析来检验特定假设，即这些电流特性的年龄相关变化导致放电率增加。在目标2中，电压钳记录将评估这些细胞中的谷氨酸能和GABA能突触后电流的年龄相关变化，测试突触传递变化与信号改变相关的特定假设。目的3实验将探索与年龄相关的变化，详细的树突状结构和树突棘的LY填充层3锥体细胞，测试的具体假设，改变形态结构的基础上的变化，这些细胞的信号传导特性。来自这些目标中的每一个的数据将是交叉相关的，并且还与老年猴组内的认知表现评分相关。这种多方面的方法将提供关于正常老化对个体神经元内不同但相互关联的细胞特性的影响的独特信息，这些细胞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至关重要，也是未来开发治疗干预措施的先决条件。

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.