Integrin and LTP Consolidation

整合素和LTP巩固长时程增强（如果在诱导后几分钟内施加低频传入刺激，则LTP消失。 这种效应是突触特异性的，并且当施加于非增强突触时，逆转刺激仅具有瞬时效应。缺氧、冷却或腺苷输注也可逆转增强作用。 LTP在其诱导后的30分钟内变得越来越不容易受到破坏，这一时间范围与许多实验范式中的记忆“巩固”相当。 拟议的工作测试的假设，整合素，异源二聚体跨膜粘附受体的家庭，发挥关键作用的稳定（或“巩固”）的LTP。 整合素是潜伏的，直到呈现适当的激活刺激。 活化的整合素结合细胞外基质，重组膜下细胞骨架，并启动信号级联反应。 阻断整联蛋白-基质结合的小肽对LTP的初始阶段没有明显的影响，但在1-2小时的时间内使增强稳定地向基线衰减。 拟定研究的第一个目的是检验以下预测：不同的整联蛋白拮抗剂将以与其阻断基质结合的相对效力相对应的相对效力阻断LTP巩固。 预计这些实验还将提供关于哪些整合素参与LTP以及它们是否参与巩固过程的不同阶段的信息。 第二个目的是映射整合素在海马区CA 1的分布。 原位杂交、免疫细胞化学和共沉淀研究的结果表明，海马中表达4-6种整合素。 光镜和电子显微镜实验的组合将用于确定这些受体在树突状区域内重叠的程度。 第三个目标是测试用于诱导LTP的θ模式刺激将激活海马整合素的预测。 将使用粘着斑激酶（FAK）自磷酸化的免疫细胞化学试验检测整联蛋白活化。 还将进行阻断LTP的整联蛋白拮抗剂是否也减少由θ刺激引起的FAK磷酸化的测试。 第四个目的是测试先前报道的促进或延迟LTP稳定的调节性受体是否也促进或延迟NMDA受体对整联蛋白的激活。 预计这四组研究将有助于阐明LTP的一个关键但知之甚少的方面，为增强效应如何表达的想法提供新的限制，并产生关于记忆基本属性的新假设。

Integrins and LTP consolidation Long term potentiation (LTP disappears if low frequency afferent stimulation is applied within a few minutes of induction. This effect is synapse specific and the reversing stimulation has only transient effects when applied to unpotentiated synapses. Potentiation is also reversed by hypoxia, cooling, or adenosine infusions. LTP becomes progressively less vulnerable to disruption during the 30 minutes following its induction, a time frame comparable to that for memory 'consolidation' in many experimental paradigms. The proposed work tests the hypothesis that integrins, a family of heterodimeric transmembrane adhesion receptors, play a critical role in the stabilization (or 'consolidation') of LTP. Integrins are latent until presentation of an appropriate activating stimulus. Activated integrins bind to the extracellular matrix, reorganize the submembrane cytoskeleton, and initiate signaling cascades. Small peptides that block integrin-matrix binding have no evident effects on the initial stages of LTP but cause potentiation to decay steadily towards baseline over a period of 1-2 hours. The first objective of the proposed studies is to test the prediction that diverse integrin antagonists will block LTP consolidation with relative potencies that correspond to their relative potencies in blocking matrix binding. It is expected that these experiments will also provide information on which integrins are involved in LTP and whether they are engaged at different phases of the consolidation process. The second objective is to map the distribution of integrins in hippocampal field CA1. Results from in situ hybridization, immunocytochemical, and co-precipitation studies suggest that 4-6 integrins are expressed in hippocampal. A combination of light and electron microscopic experiments will be use to determine the extent to which these receptors overlap within dendritic fields. The third objective is to test the prediction that the theta patterns stimulation used to induce LTP will activate hippocampal integrins. Immunocytochemical assays for autophosphorylation of the focal adhesion kinase (FAK) will be used to test for integrin activation. Tests of whether integrin antagonists that block LTP also reduce the FAK phosphorylation elicited by theta stimulation will also be conducted. The fourth objective is to test if modulatory receptors previously reported to promote or retard the stabilization of LTP also promote or retard integrin activation by NMDA receptors. It is expected that the four groups of studies will help elucidate a critical but poorly understood aspect of LTP, provide new constraints on ideas about how the potentiation effect is expressed, and generate novel hypotheses about a fundamental property of memory.