The Essential Role of Presynaptic NMDA Receptors in The Fast Antidepressant Actions of Ketamine and Its Metabolite

项目摘要/摘要 来自临床试验和动物实验的证据表明，单次亚麻醉剂量的 氯胺酮能产生快速的抗抑郁反应。然而，精神分裂的性质 和滥用氯胺酮的可能性，在推广这种化合物用作 抑郁症的一般治疗。关于快速反应的机制的报告 氯胺酮的抗抑郁作用存在争议。尤其是，目前还不确定 分子事件介导氯胺酮或其代谢产物增强兴奋性突触的作用 变速箱。在初步实验中，观察到氯胺酮及其代谢物， 顺式-6-HNK，有效增强Shaffer侧枝循环-CA1(SC-CA1)EPSCs和fEPSP。这些 动作可被MK-801模拟并完全阻断，但不能被GABA消除 受体阻断。氯胺酮有效地增加了总和表面GluA1的表达，并 GluA1 Ser845位点的磷酸化。此外，氯胺酮不能增强SC-CA1的fEPSP 并在GluA1 S845A敲入小鼠中诱导抗抑郁药样反应。此外， 完全消除CA3神经元上NMDA受体的缺失，而不是CA1细胞上的NMDA受体缺失 氯胺酮对SC-CA1突触传递的增强作用在提议的项目中 实验旨在测试GluA1 Ser845磷酸化和突触前的作用 氯胺酮和HNK中的NMDA受体产生快速作用的抗抑郁反应，如 以及它们的细胞和分子碱基。电生理技术将结合在一起， 包括采用Western blotting等细胞生物学技术的全细胞膜片钳， 表面蛋白和GluR1 S845A敲入小鼠的生物素化，CA1细胞或CA3细胞特异性 NR1基因敲除小鼠、HCN1基因敲除小鼠以及行为测量 设计实验。拟议的项目将扩大知识，了解 氯胺酮快速抗抑郁作用的细胞机制。更好地理解 氯胺酮的快速抗抑郁作用将推动设计新一代 快速有效的抗抑郁药，为抑郁症提供更好的治疗。

Project Summary/Abstract Evidence from clinical trials and animal experiments shows a single subanesthesia dose of ketamine produces rapid antidepressant responses. However, the psychotomimetic properties and abuse potential of ketamine necessitate caution in promoting this compound to be used as a general treatment of depression. The reports on the mechanisms underlying the rapid-acting antidepressant effects of ketamine are controversial. Particularly, it remains uncertain which molecular events mediate ketamine’s or its metabolites’ action in enhancing excitatory synaptic transmission. In preliminary experiments, it was observed that both ketamine and its metabolite, cis-6-HNK, potently enhanced Shaffer collateral-CA1 (SC-CA1) EPSCs and fEPSPs. These actions were mimicked and completely occluded by MK-801, but not eliminated by GABA receptor blockade. Ketamine potently increased total and surface GluA1 expression and the phosphorylation of GluA1 Ser845 site. In addition, ketamine failed to potentiate SC-CA1 fEPSPs and induce the antidepressant-like responses in GluA1 S845A knock-in mice. Furthermore, deletion of NMDA receptor on CA3 neurons but not on CA1 cells completely eliminated ketamine-induced potentiation on SC-CA1 synaptic transmission. In the proposed project experiments are designed to test the role of GluA1 Ser845 phosphorylation and presynaptic NMDA receptors in ketamine- and HNK-produced rapid-acting antidepressant responses as well as their celluar and molecular bases. Electrophysiological techniques will be combined, including whole-cell patch clamp with cell biological technique such as Western blotting, biotinylation of surface proteins and GluR1 S845A knock-in mice, CA1 cell- or CA3 cell-specific NR1 knockout mice, HCN1 knockout mice as well as behavioral measurements to achieve the designed experiments. The proposed project will expand knowledge in understanding the cellular mechanisms of fast-acting antidepressant actions of ketamine. A better understanding of ketamine’s fast-acting antidepressant effects will promote the design of a new generation of rapid-acting antidepressant to offer a better therapy to depression.