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

描述(由申请者提供)：随着年龄的增长，往往伴随着认知障碍，其特征是学习和记忆方面的严重缺陷。这些赤字对日常生活产生了不利影响，降低了生活质量，并给受影响的人及其家人带来了经济和社会负担。导致这些年龄相关损伤的确切神经机制仍不清楚。然而，使用各种模型系统的实验数据表明，神经元钙稳态的失调是这些认知障碍的一个重要因素。具体地说，在神经元活动过程中观察到的神经元内钙离子[Ca~(2+)]i似乎与年龄有关。这种由活动驱动的[Ca~(2+)]i积累的增加对神经元的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。[Ca~(2+)]_i的升高是L型电压门控钙通道(L-VGCC)表达随年龄增加的结果。这导致了一种假设，即与年龄相关的L-VGCCs表达的增加导致神经元兴奋性的降低，进而降低LTP。由此导致的LTP下降扰乱了海马体编码新信息的能力。在这项提案中，我们将使用多学科方法来测试这一假设的关键要素。在特定目的I中，我们将使用L-VGCC基因敲除(KO)小鼠来确定L-VGCC是否是与年龄相关的神经元兴奋性和LTP降低所必需的。在特定目的II中，我们将利用器官型海马片培养和表位标记的重组L-VGCC孔形成亚单位，确定L-VGCC的过度表达是否足以引起神经元兴奋性和长时程增强的变化，与正常衰老时观察到的变化相似。最后，在特定目的III中，我们将利用L-VGCC KO小鼠来确定L-VGCC在多大程度上促进了通常在老年小鼠中观察到的学习和记忆障碍。这些研究的结果将为我们提供对衰老的神经生物学的有价值的见解，并将有助于确定治疗干预的靶点，旨在改善因年龄相关的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.