Slow Outward Currents and Learning In Aging Hippocampus

描述（由申请人提供）：海马体在陈述性学习的早期阶段至关重要，陈述性学习是一种在衰老过程中退化的能力，有助于与年龄相关的学习障碍。增龄过程中钙离子依赖性爆发后超极化（AHP）的增加降低了海马CA 1区锥体神经元的内在兴奋性和信息处理能力，并导致与年龄相关的学习障碍。我们的初步数据强烈表明，学习和年龄相关的AHP的变化，部分可能是直接由于Ca 2+本身的改变。静息Ca ~（2+）和内源性Ca ~（2+）缓冲能力深刻地影响神经元功能。但是，它们是否会因学习和老化而改变，成为AHP改变的机制？我们将使用Ca 2+成像技术来了解Ca 2+处理的变化对学习和衰老的AHP整体改变的潜在贡献。我们将确定的Ca 2+来源的AHP，确定是否在树突的来源有相同的影响的AHP附近的索马的来源，如果这些Ca 2+来源的学习痕迹眨眼条件反射和老化改变。学习依赖于校园的任务需要蛋白质合成。我们最近表明，在年轻的成年大鼠学习相关的AHP减少介导的部分蛋白激酶A（PKA）的活性，已知激活CREB和随后的基因转录/翻译，并减少爆发后的AHP。将继续进行系统的学习和年龄相关的蛋白质分子检测，这些蛋白质参与了导致CREB激活的亚细胞级联反应，并通过蛋白质印迹和免疫组织化学实验改变了AHP。如果年龄相关的学习障碍确实是由于扩大后爆发AHP，那么基因沉默蛋白质的表达，导致AHP减少（从而增加神经元兴奋性）应该逆转年龄相关的学习障碍。我们将使用重组腺相关病毒载体沉默特定的蛋白质表达在海马在空调。我们还将比较生物物理和Ca 2+特性的转染（标记有荧光指示剂）和未转染的CA 1神经元从治疗大鼠，以验证Ca 2+瞬变和postburst AHP减少在转染的神经元。候选基因沉默将确定从文献和分子测定在本研究计划的早期完成。我们的目标是确认AHP是内在兴奋性的关键调节器，并且有针对性的分子方法来降低老年受试者CA 1神经元中的AHP将导致成功的学习。成功将表明沉默的蛋白质是一个可行的候选目标，作为年龄相关学习障碍的治疗干预点。 公共卫生相关性：行为，钙成像，分子和生物物理实验方法将被用来调查的作用，神经元钙加工控制的学习在年轻和老龄大鼠。目标是确定从这些方法中开发的分子遗传干预是否可以逆转大鼠中与年龄相关的学习障碍。成功的实验将直接转化为人类，因为正在开发分子遗传学方法来治疗老年人的神经退行性疾病，并且海马体依赖性眨眼条件反射任务在实验动物和人类之间具有直接的相似性。

DESCRIPTION (provided by applicant): The hippocampus is critically involved in the early stages of declarative learning, a capacity degraded during aging, contributing to age-associated learning impairments. Enlarged Ca2+-dependent postburst afterhyperpolarization (AHP) during aging reduces the intrinsic excitability of CA1 pyramidal neurons as well as the information handling capacity of the CA1 region of the hippocampus and contributes to the age-associated learning impairment. Our preliminary data strongly suggest that the learning- and age-related AHP changes may, in part, be directly due to alterations in Ca2+ itself. Resting Ca2+ and endogenous Ca2+ buffering capacity profoundly influence neuronal function. But are they altered by learning and aging, serving as the mechanism by which the AHP is changed? We will use Ca2+ imaging techniques to understand the potential contribution of change in Ca2+ handling to the overall alterations in the AHP with learning and aging. We will determine the Ca2+ sources for the AHP, determine if sources in dendrites have the same impact on the AHP as sources near the soma, and if these Ca2+ sources are altered by learning trace eyeblink conditioning and aging. Learning hippocampus-dependent tasks require protein synthesis. We have recently shown that the learning-related AHP reduction in young adult rats is mediated in part by protein kinase A (PKA) activity, known to activate CREB and subsequent gene transcription/translation, and reduce the postburst AHP. Systematic learning- & age-related molecular assays for proteins involved in the subcellular cascades that lead to CREB activation and alterations in the AHP with western blot and immunohistochemistry experiments will be continued. If age related learning impairment is truly due to the enlarged postburst AHP, then genetically silencing the expression of a protein to cause AHP reduction (and thus, increase neuronal excitability) should reverse the age-related learning impairment. We will use recombinant adeno-associated viral vectors to silence specific protein expression in the hippocampus during conditioning. We will also compare the biophysical and Ca2+ properties of transfected (tagged with fluorescent indicators) and untransfected CA1 neurons from treated rats to verify that the Ca2+ transient and the postburst AHP are reduced in the transfected neurons. Candidate genes to silence will be determined from the literature and molecular assays done earlier in this research program. The goals are to confirm that the AHP is the key regulator of intrinsic excitability and that targeted molecular methods to reduce the AHP in CA1 neurons in aged subjects will lead to successful learning. Success will indicate that the protein being silenced is a viable candidate to target as a therapeutic intervention point for age-associated learning impairments. PUBLIC HEALTH RELEVANCE: Behavioral, calcium imaging, molecular and biophysical experimental approaches will be used to investigate the role of neuronal calcium processing in control of learning in young and aging rats. The goal is to determine if molecular genetic interventions developed from these approaches reverse age-associated learning impairments in rats. Successful experiments will have direct translatability to humans, as molecular genetic approaches are being developed to treat neurodegeneration in aging humans and the hippocampus dependent eyeblink conditioning task has direct parallels between experimental animals and humans.