Hippocampal Synaptic Structure

描述（由申请人提供）：这是一项长期项目的再申请，该项目涉及海马神经元在衰老过程中钙（Ca 2+）相关过程的失调以及神经元功能/脆弱性改变的后果。该项目最初源于以下发现：海马锥体神经元动作电位爆发后的Ca 2+依赖性缓慢后超极化（sAHP）在老年动物中比在成年动物中更大。重要的是，较大的sAHPs与神经元兴奋性降低和学习记忆受损相关。相反，在学习任务的动物中发现了较小的sAHPs。从那时起，我们和其他人已经确定，钙离子动作电位，钙离子瞬变和L型钙离子电流也增加，在老年神经元。这些结果导致了脑老化的Ca 2+失调假说，其中L-通道活性的增加起着关键的起始作用，并且由此产生的较大的sAHP降低了神经元的兴奋性。同样明显的是，来自兰尼碱受体（RyRs）的增强的Ca 2+诱导的Ca 2+释放（CICR）调节锥体神经元中与衰老相关的Ca 2+瞬变和sAHP的幅度。该项目的主要目标是从根本上推进我们对导致不健康大脑衰老的Ca 2+失调的潜在分子机制的理解。基于我们新的有趣的结果，我们制定了一个新的工作假设，年龄相关的Ca 2+失调，这表明免疫亲素，特别是FK-506结合蛋白1b和/或1a（FKBP 1b/1a）的下调，导致RyR不稳定，更大的CICR和更大的sAHPs级联。由此产生的影响是神经元兴奋性和行为可塑性受损。这些研究将使用病毒载体的显微注射在体内操纵FKBP-Ca 2+调节途径中FKBP 1b/1a和其他蛋白质的海马表达/功能。将使用多学科方法在相同动物中评估多种结局，包括广泛的行为测试、最先进的细胞内电生理学以及伴随的Ca 2+成像、免疫组织化学和基因微阵列分析。这些研究应充分阐明依赖于Ca 2+失调的衰老变化，并应明确测试FKBPs在衰老过程中Ca 2+失调和海马功能中的作用。慢性干预研究提出，可能有直接的翻译相关性，并直接导致新的预防和治疗方法对衰老相关的脑功能下降。鉴于老龄化人口的急剧增加，识别和开发此类疗法以维持老年人的认知功能变得越来越重要。

DESCRIPTION (provided by applicant): This is the resubmission of a renewal application for a longstanding project on dysregulation of calcium (Ca2+)-related processes in hippocampal neurons during aging and the consequences for altered neuronal function/vulnerability. The project initially derived from the finding that the Ca2+-dependent slow afterhyperpolarization (sAHP), that follows a burst of action potentials in hippocampal pyramidal neurons, is larger in aged than in young-adult animals. Importantly, larger sAHPs are correlated with reduced neuronal excitability and impaired learning and memory. Conversely, smaller sAHPs are found in animals that learn a task. Since then, we and others have determined that Ca2+ action potentials, Ca2+ transients and L-type Ca2+ currents also are increased in aged neurons. These results led to a Ca2+ dysregulation hypothesis of brain aging, in which increased activity of L-channels plays a key initiating role and the resulting larger sAHP reduces neuronal excitability. It also has become apparent that enhanced Ca2+-induced Ca2+ release (CICR) from ryanodine receptors (RyRs) modulates the magnitude of aging-related Ca2+ transients and sAHPs in pyramidal neurons. The major objective of this project is to fundamentally advance our understanding of the underlying molecular mechanisms of Ca2+ dysregulation that lead to unhealthy brain aging. Based on our new intriguing results, we have formulated a novel working hypothesis of age-related Ca2+ dysregulation that suggests that downregulation of immunophilins, particularly FK-506 binding protein 1b and/or 1a (FKBP1b/1a), leads to a cascade of RyR destabilization, greater CICR and larger sAHPs. The resulting effect is impaired neuronal excitability and behavioral plasticity. These studies will manipulate hippocampal expression/function of FKBP1b/1a and other proteins in the FKBP- Ca2+ regulatory pathway in vivo using microinjection of viral vectors. Multiple outcomes will be assessed in the same animals using a multidisciplinary approach comprising extensive behavioral testing, state-of-the-art intracellular electrophysiology with concomitant Ca2+ imaging, immunohistochemistry, and gene microarray analysis. These studies should substantially elucidate aging changes that depend on Ca2+ dysregulation and should clearly test the role of FKBPs in Ca2+ dysregulation and hippocampal function during aging. Chronic intervention studies are proposed that could have direct translational relevance and lead directly to novel preventative and therapeutic treatments against aging-related decline of brain function. Given the dramatic increase in the aging population, it is becoming increasingly important to identify and develop such therapies to maintain cognitive function in the elderly.