Synaptic Adaptation and Plasticity After Chronic Disuse

描述（由申请人提供）：突触强度必须在面对不断变化的输入水平时进行调节，以确保控制所有输入的总强度，从而将输出放电保持在合理的范围内，这些机制必须与突触可塑性机制一起工作。它的临床重要性可以通过癫痫的情况得到最好的说明，这些机制在极端情况下被破坏。癫痫与多种形式的遗传性认知功能障碍（如脆性X染色体和唐氏综合症）的关联，以及抗癫痫药物用于治疗情绪障碍的增加，突出了这些机制在维持正常脑功能方面的重要性。该资助计划在实验室最新进展的基础上，研究突触在面对不同输入水平时的适应机制，以及这种适应对可塑性的影响。前两部分将利用原代培养系统中易于操作和测量的优势，使用策略更完整地描述从突触输入到突触修饰通路中的信号事件。本研究的这一部分将首先仔细剖析负责诱导关键信号事件的电输入和钙进入的来源，然后阐明关键中间信号产物的调节机制，检查它们的酶活性、稳定性、转录、翻译和转运到突触的调节。此外，对信号级联的更完整描述将从微阵列研究中得出，这些研究比较了在不同点上信号通路中断的结果。研究的下一部分将密切关注这一现象的微生理学(a)通过比较单个细胞中网络变化和操作的影响来阐明细胞自主适应的要素(b)描述单个突触水平上的适应变化，以及(c)确定各种适应要素的突触前或突触后诱导位点。这些研究将利用实验室长期以来在研究单突触生理学方面的专业知识，包括局灶刺激和测量单一位点的突触反应。项目的最后一部分将运用在前几节中获得的知识，尝试了解适应对完整海马回路的影响，使用器官型切片培养。研究的主要问题将是在两组不同的事件中适应表达的差异，以及这种适应对LTP诱导和表达的影响。我们将寻找以前未在锥体神经元中发现的LTP形式，以及LTP先前存在机制的性能变化。

DESCRIPTION (provided by applicant): Synaptic strength must be regulated in the face of changing levels of input in order to ensure that total strength of all inputs are controlled so as to maintain output firing within reasonable limits and these mechanisms must work in conjunction with mechanisms of synaptic plasticity. Its clinical importance can be best illustrated by the condition of epilepsy where these mechanisms are disrupted at the extreme. The association of epilepsy with numerous forms of inherited disorders of cognitive function such as Fragile X and Down Syndrome and the increasing use of anti-epileptic drugs for the treatment of mood disorders highlight the importance of these mechanisms in maintaining normal brain function. This grant proposes to study the underlying mechanisms by which synaptic adaptation is achieved in the face of changing levels of input and the effects of this adaptation on plasticity, building on recent progress in the lab. The first two parts will use strategies to describe more completely the signaling events in the pathway from synaptic input to synaptic modification, taking advantage of the ease of manipulation and measurement in the primary culture system. This part of the study will begin with a careful dissection of the sources of electrical input and calcium entry responsible for the induction of the key signaling events, followed by an elucidation of the mechanisms of regulation of key intermediate signaling products, examining the regulation of their enzymatic activity, stability, transcription, translation and transport to the synapse. In addition, a more complete description of the signaling cascade will be drawn out from microarray studies comparing results from disruption of the signaling pathway at various points. The next part of the study will look closely at the microphysiology of this phenomenon (a) to elucidate the elements of adaptation that are cell-autonomous, by comparing effects of network changes and manipulations in only one cell (b) to describe adaptive changes at the level of single synapses, and (c) to determine the pre- or postsynaptic locus of induction of the various elements of adaptation. These studies will take advantage of long standing expertise in the lab in studying the physiology of single synapses involving focal stimulation and measurement of synaptic responses at unitary sites. The last part of the project will apply the knowledge gained in the previous sections to try to understand the impact of adaptation m intact hippocampal circuits, using the organotypic slice culture. Primary questions addressed will be differences in the expression of adaptation at two different sets of afferents and consequences of this adaptation on the induction and expression of LTP. We will look for forms of LTP not previously found in pyramidal neurons and for changes in the performance of preexisting mechanisms of LTP.