L-type Calcium Channels, Neuronal Excitability & Cognition in Aged Mice

描述（由申请人提供）：随着年龄的增长，通常伴有认知障碍，其特征是学习和记忆的严重缺陷。这些赤字对日常生活产生不利影响，降低生活质量，并给受影响者及其家庭带来财政和社会负担。引起这些与年龄有关的损伤的确切神经机制仍然未知。然而，来自使用各种模型系统的实验的数据表明，神经元Ca 2+稳态的失调是这些认知障碍的重要促成因素。具体而言，似乎有一个年龄相关的增加，细胞内钙[Ca 2 +]i在神经元活动期间观察到的神经元。这种活动驱动的[Ca 2 +]i积累的增加对神经元兴奋性和长时程增强（LTP）产生不利影响，这两个过程都与学习和记忆有关。已表明[Ca 2 +]i的增加是L型电压门控钙通道（L-VGCC）表达的年龄相关性增加的结果。这导致了一种假设，即L-VGCC表达的年龄相关性增加导致神经元兴奋性降低，这反过来又降低了LTP。由此导致的LTP的减少破坏了海马体编码新信息的能力。在本提案中，我们将使用多学科方法来测试这一假设的关键要素。在具体目标I中，我们将使用L-VGCC敲除（KO）小鼠来确定L-VGCC是否是神经元兴奋性和LTP年龄相关性降低所必需的。在特定目标II中，使用器官型海马切片培养物和表位标记的重组L-VGCC孔形成亚基，我们将确定L-VGCC的过度表达是否足以产生与正常衰老期间观察到的相似的神经元兴奋性和LTP变化。最后，在具体目标III中，我们将利用L-VGCC KO小鼠来确定L-VGCC在多大程度上有助于老年小鼠中通常观察到的学习和记忆缺陷。这些研究的结果将为我们提供对衰老神经生物学的有价值的见解，并将有助于确定治疗干预的目标，旨在改善因年龄相关钙稳态改变而引起的认知障碍。

DESCRIPTION (provided by applicant): Advancing age is often accompanied by cognitive impairments characterized by substantial deficits in learning and memory. These deficits adversely effect day to day living, reduce the quality of life and impose a financial and social burden on the affected and their families. The exact neuronal mechanism that gives rise to these age-related impairments remains unknown. However, data from experiments using a variety of model systems, suggests that dysregulation of neuronal Ca2+ homeostasis is a significant contributing factor to these cognitive impairments. Specifically, there appears to be an age-related increase in intracellular calcium [Ca2+]i in neurons observed during neuronal activity. This increase in activity-driven accumulation of [Ca2+]i adversely impacts neuronal excitability and long-term potentiation (LTP), processes that have both been implicated in learning & memory. It has been suggested that the increase in [Ca2+]i is the result of an age-related increase in expression of L-type voltage-gated calcium channels (L-VGCCs). This has led to the hypothesis that an age-related increase in L-VGCCs expression leads to a decrease in neuronal excitability which in turn reduces LTP. The resulting decrease in LTP disrupts the ability of the hippocampus to encode new information. In this proposal we will use a multidisciplinary approach to test key elements of this hypothesis. In Specific Aim I we will use L-VGCC knockout (KO) mice to determine whether L-VGCCs are necessary for the age-related decrease in neuronal excitability and LTP. In Specific Aim II, using organotypic hippocampal slice cultures and epitope-tagged recombinant L-VGCC pore forming subunits, we will determine whether over-expression of L-VGCCs is sufficient to produce changes in neuronal excitability and LTP similar to that observed during normal aging. Finally, in Specific Aim III we will utilize L-VGCC KO mice to determine to what extent L-VGCCs contribute to the learning & memory deficits normally observed in aged mice. Results from these studies will provide us with valuable insights into the neurobiology of aging and will aid in the identification of targets for the therapeutic intervention, designed to ameliorate cognitive impairments that arise from alterations in age-related calcium homeostasis.