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，通常伴随着认知障碍，其特征是学习和记忆方面的严重缺陷。这些缺陷对日常生活产生不利影响，降低了生活质量，并给受影响的人及其家庭带来了经济和社会负担。导致这些与年龄相关的损伤的确切神经元机制尚不清楚。然而，使用各种模型系统的实验数据表明，神经元Ca2+稳态失调是导致这些认知障碍的重要因素。具体来说，在神经元活动期间观察到的神经元细胞内钙[Ca2+]i似乎与年龄相关。这种活动驱动的[Ca2+]i积累的增加对神经元兴奋性和长期增强（LTP）产生不利影响，这两个过程都与学习和记忆有关。研究表明，[Ca2+]i的增加是l型电压门控钙通道（L-VGCCs）表达与年龄相关的增加的结果。这导致了一种假设，即与年龄相关的l - vgc表达增加导致神经元兴奋性降低，从而降低LTP。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检验这一假设的关键要素。在Specific Aim I中，我们将使用L-VGCC敲除（KO）小鼠来确定L-VGCC是否对与年龄相关的神经元兴奋性和LTP下降是必要的。在Specific Aim II中，我们将使用器官型海马切片培养和表位标记的重组L-VGCC孔隙形成亚基，确定L-VGCC的过表达是否足以产生与正常衰老过程相似的神经元兴奋性和LTP的变化。最后，在Specific Aim III中，我们将利用L-VGCC KO小鼠来确定L-VGCC在多大程度上导致了老年小鼠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有关衰老的神经生物学的宝贵见解，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.