Dissecting the Contribution of the Ventral Hippocampus to (R,S)-Ketamine's Fear Buffering Effects

项目摘要/摘要 虽然压力对于物种的适应生存是必要的，但暴露在压力之下也会导致适应不良。 生理和行为反应。应激诱导的适应不良反应可能导致随后的 精神障碍的发展，如创伤后应激障碍(PTSD)和严重抑郁 精神障碍(MDD)。在这些障碍中观察到的一个核心症状是恐惧表达的增加，如 在存在与恐惧相关的刺激时，恐惧反应增强。我们之前已经发现， 一次注射(R，S)-氯胺酮，一种快速起作用的抗抑郁药，减轻学习后的恐惧 恐惧条件反射(CFC)。我们和其他人已经报道了腹侧海马体(VHPC)，特别是 腹侧CA3(VCA3)介导(R，S)-氯胺酮减轻习得性恐惧的作用。然而，到底是如何 (R，S)-氯胺酮调节vCA3中的集合以减少恐惧，推广仍有待探索。它有 此外，研究还表明，腹侧CA1(VCA1)与恐惧行为有关。因此，这项研究计划将制定 揭示(R，S)-氯胺酮对体内使用恐惧行为影响的基础 微透析补充和进一步解释已经从vCA3体内钙离子成像收集的数据 和vCA1。总的来说，我这个提议的目标是更好地了解(R，S)-氯胺酮是如何改变的 神经递质和神经元集合，以缓冲加剧的恐惧表达。我的初选 目标1中概述的研究结果表明，(R，S)-氯胺酮：1)在恐惧编码过程中钝化对电击的反应 特别是在vCA3中；2)不同地影响海马腹侧区CA3和CA1的活动；以及3) 在恐惧编码和提取过程中，减少腹侧海马区的相关活动。一起， 这些发现引出了我的假设，即神经递质含量有明显的变化 紧随其后(右，S)-氯胺酮注射，持久，钝化的经验 可怕的压力源。然而，为了验证这一假设，我需要利用目标2中概述的体内微透析 测定vCA3或vCA1中谷氨酸、γ-氨基丁酸(GABA)和5-羟色胺(5-HT)的水平 雄性和雌性小鼠了解它们如何潜在地调节(R，S)-氯胺酮的影响。到目前为止，没有 利用体内钙离子成像或体内微透析研究的纵向研究尚未进行 研究(R)-氯胺酮对恐惧行为的影响。在目标3中，我描述了一个博士后研究方向 完成我的目标，了解压力恢复能力的生物学基础。我在以下方面积累了经验 行为学、活体技术、细胞和分子神经科学以及显微镜。然而，我还没有 操纵电路的技术，或探测药物后转录变化的贡献的技术 治疗或应对压力。因此，我计划通过寻找一位博士后来解决我知识上的这些差距 这个职位能让我在这些技能上有所成长。总之，这项提议将导致制定一项 不同的技能，以成为精神病学领域的成功独立研究人员。

PROJECT SUMMARY / ABSTRACT Though stress is necessary for the adaptive survival of a species, stress exposure can also elicit maladaptive physiological and behavioral responses. Stress-induced maladaptive responses may lead to subsequent development of psychiatric disorders such as post-traumatic stress disorder (PTSD) and major depressive disorder (MDD). A core symptom observed in these disorders is increased fear expression, as defined by heightened fear responses in the presence of stimuli associated with fear. We have previously discovered that a single injection of (R,S)-ketamine, a rapid-acting antidepressant, attenuates learned fear following contextual fear conditioning (CFC). We and others have reported that the ventral hippocampus (vHPC), specifically ventral CA3 (vCA3), mediates (R,S)-ketamine’s effects on attenuating learned fear. However, how exactly (R,S)-ketamine modulates the ensembles in vCA3 to decrease fear generalization is yet to be explored. It has additionally been shown that ventral CA1 (vCA1) contributes to fear behavior. Thus, this research plan will lay the groundwork to uncover the effects of (R,S)-ketamine administration on fear behavior using of in vivo microdialysis to complement and further explain the data already collected from in vivo Ca2+ imaging in vCA3 and vCA1. Overall, my goal for this proposal is to better understand how (R,S)-ketamine alters neurotransmitters and neuronal ensembles to buffer against heightened fear expression. My preliminary findings outlined in Aim 1 show that (R,S)-ketamine: 1) blunts responses to shocks during fear encoding specifically in vCA3; 2) differentially affects activity in ventral hippocampal regions CA3 and CA1; and 3) decreases correlated activity in the ventral hippocampus during both fear encoding and retrieval. Together, these findings lead me to my hypothesis that there are distinct changes in neurotransmitter content immediately following (R,S)-ketamine administration that are long-lasting and that blunt the experience of a fearful stressor. However, to test this hypothesis, I need to utilize in vivo microdialysis as outlined in Aim 2 to measure levels of glutamate, gamma-aminobutyric acid (GABA), and serotonin (5-HT) in vCA3 or vCA1 of male and female mice to understand how they potentially mediate (R,S)-ketamine’s effects. To date, no longitudinal studies utilizing in vivo Ca2+ imaging or in vivo microdialysis studies have yet been performed investigating (R,S)-ketamine effects on fear behavior. In Aim 3, I describe a postdoctoral research direction to accomplish my goal of understanding the biological substrates of stress resilience. I have gained experience in behavior, in vivo techniques, cellular and molecular neuroscience, and microscopy. However, I have yet to conduct techniques that manipulate circuits, or that probe the contribution of transcriptomic changes after drug treatment or with stress. Thus, I plan to address these gaps in my knowledge by finding a post-doctoral position that allows me to grow in these skills. In summary, this proposal will lead to the development of a diverse skillset in order to become a successful independent researcher in the psychiatric field.