Synaptic Homeostasis in Neocortical Neurons

描述（由申请人提供）： 在学习和发育过程中，神经回路通过突触数量和强度的变化而得到改善。大多数关于长时程突触可塑性的研究都集中在突触特异性的可塑性形式，如长时程增强（LTP）。虽然LTP对神经元回路的完善可能很重要，但它可能还不够，因为它往往会破坏神经元网络的活动。我们已经集中我们的努力，了解突触可塑性机制，稳定神经元的活动，面对突触数量和强度的持续变化。在过去的几年里，我们一直在研究突触缩放的机制和功能-一种形式的稳态突触可塑性-使用来自出生后的视觉皮层的培养系统。尽管近4年来对稳态突触可塑性的研究越来越多，但关于其机制和功能仍有许多未解之谜。在这个更新的应用程序中，我们希望检查参与突触前和突触后机制的表达突触缩放，并解开突触前和突触后活动的相对贡献，在诱导突触缩放。我们将结合电生理学、定量免疫组织化学和时间推移成像方法来量化突触后AMPA受体积累的变化。使用RNAi选择性地减少单个AMPAR亚基的表达，我们将确定哪些亚基在突触缩放期间被靶向插入。我们将确定是否有突触前递质释放的互补变化，以及是否postsynatpic和突触前机制是时间和因果关系相关或独立发生。最后，我们将询问突触缩放是否是由突触前输入功效的局部变化引起的，或者是突触后活动的全局函数。除了对活动依赖性可塑性产生重要的机制性见解外，这些实验还将测试关于突触缩放功能的一些基本假设。

DESCRIPTION (provided by applicant): During learning and development, neural circuitry is refined through changes in synapse number and strength. Most studies of long-term synaptic plasticity have focused on synapse-specific forms of plasticity such as long-term potentiation (LTP). While LTP is likely important for the refinement of neuronal circuitry, it probably not sufficient, because it tends to destabilize the activity of neuronal networks. We have concentrated our efforts on understanding the synaptic plasticity mechanisms that stabilize neuronal activity in the face of ongoing changes in synapse number and strength. For the past several years we have been studying the mechanism and function of synaptic scaling - a form of homeostatic synaptic plasticity - using a culture system derived from postnatal visual cortex. Despite increasing study of homeostatic synaptic plasticity over the past 4 years, there are many unanswered questions about its mechanism and function. In this renewal application we wish to examine the involvement of presynaptic and postsynaptic mechanisms in the expression of synaptic scaling, and to disentangle the relative contributions of presynaptic and postsynaptic activity in the induction of synaptic scaling. We will use a combination of electrophysiological, quantitative immunohistochemical, and time-lapse imaging methods to quantify changes in postsynaptic AMPA receptor accumulation. Using RNAi to selectively reduce expression of individual AMPAR subunits we will determine which subunits are targeted for insertion during synaptic scaling. We will determine whether there are complementary changes in presynaptic transmitter release, and whether postsynatpic and presynaptic mechanisms are temporally and causally related or occur independently. Finally, we will ask whether synaptic scaling is induced by local changes in efficacy of presynaptic inputs, or is a global function of postsynaptic activity. In addition to generating important mechanistic insights into activity-dependent plasticity, these experiments will test some fundamental assumptions about the function of synaptic scaling.