Structural plasticity basis of fast-acting antidepressant action

项目摘要 单次亚麻醉剂量的氯胺酮，一种N-甲基-D-天冬氨酸受体拮抗剂，导致快速- 抗抑郁作用在啮齿动物模型中，全身氯胺酮给药与较高的 额叶皮质树突棘密度，反映了可能是行为的基础结构重塑 变化然而，在体内树突棘的更新是一个动态的过程。时间进程和特异性 氯胺酮对结构可塑性影响尚不清楚。在初步研究中，我们使用了纵向两个- 用光子显微镜反复观察小鼠内侧额叶中的同一组树突状分支 在单次注射氯胺酮或生理盐水之前和之后的皮质。我们的数据表明， 与氯胺酮给药相关的密度是由棘形成速率升高驱动的， 这些新形成的刺的一部分变得持久。但是这些额外的突触有什么特别之处呢？在 在这个提议中，我们将测试棘是随机形成的还是在特定的树突位置形成的，例如优先 突触后的特定轴突输入或在网站受到慢性压力。在目标1中，我们将测试 氯胺酮优先恢复丘脑皮层突触。我们将采用一种新的病毒策略来标记轴突 体内的钮扣。我们将量化氯胺酮对内侧额叶皮层树突棘转换的影响。 皮质，重点是突触后棘荧光标记的丘脑皮质或胼胝体输入。在目标2中， 将测试克他命是否优先逆转社会压力引起的突触缺陷。我们将描述 慢性社交失败和氯胺酮对额叶皮层结构可塑性的交互作用。 完成这些目标将把快速起效的抗抑郁药与特定连接的逆转联系起来， 压力导致的缺陷。通路特异性突触的恢复可能是一种新的机制， 抗抑郁作用，在电路水平上运作。

PROJECT SUMMARY A single subanesthetic dose of ketamine, an N-methyl-D-aspartate receptor antagonist, leads to fast- acting antidepressant effects. In rodent models, systemic ketamine administration is associated with higher dendritic spine density in the frontal cortex, reflecting structural remodeling that could underlie the behavioral changes. However, turnover of dendritic spines is a dynamic process in vivo. The time course and specificity of ketamine's effect on structural plasticity remain unclear. In preliminary studies, we used longitudinal two- photon microscopy to repeatedly visualize the same set of dendritic branches in the mouse medial frontal cortex before and after a single injection of ketamine or saline. Our data suggest that the higher dendritic spine density associated with ketamine administration is driven by an elevated rate of spine formation, and that a fraction of these newly formed spines becomes persistent. But what is special about these added synapses? In this proposal, we will test whether spines form at random or at particular dendritic locations, e.g. preferentially postsynaptic to particular axonal inputs or at sites affected by chronic stress. In Aim 1, we will test whether ketamine preferentially restores thalamocortical synapses. We will adapt a novel viral strategy to label axonal boutons in vivo. We will quantify effects of ketamine on in vivo dendritic spine turnover in the medial frontal cortex, focusing on spines postsynaptic to fluorescently tagged thalamocortical or callosal inputs. In Aim 2, we will test whether ketamine preferentially reverses social stress-induced synaptic deficits. We will characterize the interactive effects of chronic social defeat and ketamine on structural plasticity in the frontal cortex. Completing these aims would link rapidly acting antidepressants to reversals of specific connectivity and stress-induced deficits. Restoration of pathway-specific synapses could be a novel mechanism for antidepressant action that operates at the circuit level.