Effect of GABAergic inhibition of dendritic spines on synaptic pruning in the medial prefrontal cortex during adolescence

树突棘 GABA 能抑制对青春期内侧前额叶皮层突触修剪的影响

• 批准号: 10292964
• 负责人: Sheryl S Smith
• 金额: $ 62.92万
• 依托单位: SUNY DOWNSTATE MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-12-06 至 2023-10-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10292964
• 关键词: 3-Dimensional; Acute; Address; Adolescence; Adolescent; Adult; Age; Agonist; Allopregnanolone; Anatomy; Behavioral; Biological Assay; Brain; Calcium; Chronic; Clinical; Cognition; Cognitive deficits; Data; Dendritic Spines; Development; Disease; Electrophysiology (science); Genes; Genetic; Golgi Apparatus; Hippocampus (Brain); Image; Impaired cognition; Impairment; Laboratories; Learning; Link; Maintenance; Measures; Medial; Mediating; Mental disorders; Monitor; Morphology; Mus; N-Methyl-D-Aspartate Receptors; Neurons; Neuropsychology; Pharmaceutical Preparations; Pharmacology; Play; Population; Prefrontal Cortex; Process; Property; Proteins; Puberty; Pyramidal Cells; Receptor Activation; Reporting; Role; Schizophrenia; Short-Term Memory; Signal Transduction; Single Nucleotide Polymorphism; Steroids; Stress; Symptoms; Synapses; Techniques; Testing; Vertebral column; autism spectrum disorder; awake; base; behavioral outcome; behavioral plasticity; density; experimental study; flexibility; functional outcomes; gamma-Aminobutyric Acid; genetic manipulation; in vivo; in vivo calcium imaging; in vivo two-photon imaging; knock-down; novel; novel therapeutic intervention; prepuberty; receptor; response; sex; synaptic pruning; transmission process; two-photon; visual stimulus

Dendritic spines undergo synaptic pruning in the medial prefrontal cortex (mPFC) during adolescence, a process which is excessive in schizophrenia, believed to underlie cognitive impairment. Despite its importance, the mechanism underlying synaptic pruning in the mPFC is not known. Our preliminary findings suggest that extrasynaptic α4βδ GABAA receptors (GABARs), which transiently emerge on the spine at puberty onset (~PND 35) for 10d, trigger adolescent synaptic pruning in the mPFC. These receptors generate a shunting inhibition which impairs NMDA receptor activation. Our previous findings in CA1 hippocampus established that the inhibition generated by these receptors reduces expression of the Rho-GEF spine protein Kalirin-7, necessary for spine maintenance, via this reduced NMDA receptor activity. We will test the hypothesis that similar effects on spine proteins play a role in adolescent pruning in mPFC. The proposed aims will use multiple techniques, including in vivo two-photon imaging, electrophysiological, pharmacological, and immunocytochemical assays. To this end, we will chronically manipulate α4βδ function during adolescence (~PND 35-44) and quantify spine density at 8 and 12 wks of age. Preliminary data shows that spine density is decreased in both layer 3 and 5 post- pubertally in +/+ but not α4-/- mice, implicating α4βδ GABARs. Because synaptic GABAergic input targets the spine in the cortex, the role of α1β2γ2 GABARs will also be examined. These experiments will use acute pharmacological (agonists, modulators) and genetic manipulation (global/conditional/local knock-down) of α4βδ and α1β2γ2 to explore the role of these receptors in regulating spine density and morphology assessed using Golgi and electrophysiological techniques. To explore the effect of this pruning on circuit and behavioral plasticity, in vivo two-photon techniques in combination with multi- neuron recording will be used to image the Ca++ signals and record activity generated by neuronal ensembles in response to visual stimuli in the awake mouse across adolescence and after GABAR modulation/knock-down. We will thus assess the effect of pubertal α4βδ GABARs and GABAR- generated pruning on circuit function, including the power and synchronization of theta and gamma oscillations as well as on circuit activity/synchronization of ensembles and mPFC-dependent learning tasks. The findings from the proposed studies will directly address the functional role of GABAergic inhibition on dendritic spines at puberty, and will also provide mechanisms for the process of synaptic pruning, as well as explore functional outcomes of alterations in this process. These results are relevant for schizophrenia where excessive synaptic pruning and impaired working memory are reported in association reduced power/sychronization of visually-evoked gamma oscillations, and where single nucleotide polymorphisms of the δ gene are reported, suggesting a genetic link.

青春期期间，内侧前额皮质（mPFC）的树突棘经历突触修剪， 尽管存在精神分裂症的这种过度过程，但仍被认为是认知障碍的原因。 重要的是，mPFC 中突触修剪的机制尚不清楚。 研究结果表明，突触外 α4βδ GABAA 受体 (GABAR) 短暂地出现在 青春期开始时 (~PND 35) 的脊柱持续 10 天，触发 mPFC 中的青少年突触修剪。 受体产生分流抑制，损害 NMDA 受体激活。 在 CA1 海马体中，这些受体产生的抑制作用降低了 Rho-GEF 脊柱蛋白 Kalirin-7，通过这种减少的 NMDA 受体维持脊柱所必需 我们将检验脊柱蛋白的类似作用在青少年中发挥作用的假设。 mPFC 中的修剪提出的目标将使用多种技术，包括体内双光子。 为此，我们将进行成像、电生理学、药理学和免疫细胞化学测定。 在青春期 (~PND 35-44) 长期操纵 α4βδ 功能并量化 8 时的脊柱密度 12 周龄时，初步数据显示，第 3 层和第 5 层的脊柱密度均有所下降。 青春期在 +/+ 小鼠中，但在 α4-/- 小鼠中则不然，这涉及 α4βδ GABAR，因为突触 GABA 能输入。 以皮质中的脊柱为目标，α1β2γ2 GABAR 的作用也将得到检验。 将使用急性药理学（激动剂、调节剂）和基因操作（全局/条件/局部 α4βδ 和 α1β2γ2 的敲低）探索这些受体在调节脊柱密度和 使用高尔基体和电生理技术评估形态学来探讨其效果。 电路和行为可塑性的修剪，体内双光子技术与多光子技术相结合 神经记录将用于对 Ca++ 信号进行成像并记录神经产生的活动 青春期和 GABAR 之后清醒小鼠对视觉刺激的反应 因此，我们将评估青春期 α4βδ GABAR 和 GABAR- 的作用。 对电路功能进行生成修剪，包括 theta 和 gamma 的功率和同步 振荡以及电路活动/整体同步和 mPFC 相关学习 拟议研究的结果将直接解决 GABAergic 的功能作用。 对青春期树突棘的抑制，也将为突触过程提供机制 修剪，以及探索此过程中改变的功能结果这些结果是相关的。 对于精神分裂症，据报道过度的突触修剪和工作记忆受损 关联降低了视觉诱发的伽玛振荡的功率/同步性，并且在单个 据报道，δ 基因的核苷酸多态性表明存在遗传联系。