Regulation of Synaptic Plasticity in Hippocampus In Vivo

描述(申请人提供)：学习和记忆背后的神经生物学事件可能包括大脑结构中已知的削弱记忆的突触强度的活动依赖的修饰。被认为有助于记忆的使用依赖型突触修改的例子是海马区兴奋性突触的突触传递的长时程增强(LTP)和长时程抑制(LTD)。海马区LTD类似于海马区LTP，在体内CA1区持续存在数天。LTD的持久性表明，潜在的分子机制涉及基因表达的改变，尽管一些表达的变化肯定不同于LTP所涉及的变化。这项拟议的工作通过研究丝氨酸/苏氨酸蛋白磷酸酶PP1和PP2A以及细胞外信号调节激酶(ERK)级联在LTD和LTP区CA1区的作用来解决这一问题。 基于我们实验室以前的工作和其他人的工作，我们建议追求以下具体目标：(1)确定PP1或PP2A是否是LTD期间转录因子CREB活性降低的原因并在LTD的持续中起作用：(2)确定LTD是否需要从头转录和翻译，并与ERK/ELK-L介导的基因表达增加有关，而与CREB介导的表达无关；(3)探讨ERK在LTD与LTP的CREB和ELK-1功能调节中的作用，以及LTP时CREB上磷酸酶活性的降低是否有助于LTP的持续。我们将结合体内电生理技术、酶活性分析、Western印迹和免疫组织化学分析以及原位杂交来解决这些问题。总之，这些研究将阐明转录信号的负向和正向调节机制，以响应体内成年海马区可塑性诱导的突触激活，并将产生不同信号事件之间的相互作用如何结合在双向突触可塑性调节中的模型。这些研究的发现将为未来将双向突触可塑性中涉及的信号事件与行为动物执行的不同类型记忆操作中涉及的信号事件联系起来的工作奠定基础。

DESCRIPTION (provided by applicant): The neurobiological events that underlie learning and memory likely include activity-dependent modification of synaptic strength in brain structures known to subserve memory. Examples of use-dependent synaptic modification hypothesized to contribute to memory are long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission at excitatory synapses in the hippozampus. Hippocampal LTD, similar to hippocampal LTP, is persistent, lasting for days in area CA1 in vivo. The persistence of LTD suggests that the underlying molecular mechanisms involve altered gene expression, although some of the changes in expression must differ from those involved in LTP. The proposed work addresses this issue by examining the role of the serine/threonine protein phosphatases PP1 and PP2A and that of the extracellular signal-regulated kinase (ERK) cascade in LTD and LTP in area CA1 in vivo. Motivated by previous work from our laboratory and work by others, we propose to pursue the following Specific Aims: (1) To determine whether PP1 or PP2A is responsible for decreased activation of the transcription factor CREB during LTD and plays a role in the persistence of LTD; (2) To determine whether LTD requires de novo transcription and translation and is associated with an increase in ERK/Elk-l-mediated gene expression but not in CREB-mediated expression; and (3) To delineate the role of ERK in the regulation of CREB and Elk-1 function in LTD vs. LTP, and test whether reduced phosphatase action on CREB during LTP contributes to the persistence of LTP. We will address these questions with a combination of in vivo electrophysiological techniques, enzyme activity assays, Western blot and immunohistochemical analyses, and in situ hybridization. Collectively, the studies will elucidate mechanisms of negative and positive regulation of transcriptional signals in response to plasticity-inducing synaptic activation in the adult in vivo hippocampus, and will yield models of how interactions among different signaling events combine in the regulation of bidirectional synaptic plasticity. The findings from these studies will provide the foundation for future work directed at relating signaling events involved in bidirectional synaptic plasticity to signaling events involved in different types of memory operations performed by behaving animals.