Gisabella Barbara, Scammell Thomas, Bandaru Sathyajit S, Saper Clifford B
Department of Neurology, Division of Sleep Medicine, and Program in Neuroscience, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Department of Anatomy and Neurobiological Sciences, University of Mississippi Medical Center, Jackson, Mississippi.
J Comp Neurol. 2020 Feb 15;528(3):380-388. doi: 10.1002/cne.24764. Epub 2019 Sep 9.
Accumulating evidence supports the role of sleep in synaptic plasticity and memory consolidation. One line of investigation, the synaptic homeostasis hypothesis, has emphasized the increase in synaptic strength during waking, and compensatory downsizing of (presumably less frequently used) synapses during sleep. Conversely, other studies have reported downsizing and loss of dendritic spines following sleep deprivation. We wanted to determine the effect of sleep deprivation on dendritic spines of hippocampal CA1 neurons using genetic methods for fluorescent labeling of dendritic spines. Male Vglut2-Cre mice were injected with an AAV-DIO-ChR2-mCherry reporter in CA1 hippocampus. Gentle handling was used to sleep deprive mice for 5 hr, from lights on (7 am) to 12 noon. Control and sleep-deprived mice were euthanized at 12 noon and processed for quantification of dendritic spines. We used confocal microscope imaging and three-dimensional (3D) analysis to quantify thin, mushroom, and stubby spines from CA1 dendrites, distinguishing between branch segments. We observed significantly greater density of spines in CA1 of sleep-deprived mice, driven primarily by greater numbers of thin spines, and significantly larger spine volume and head diameter. Branch and region-specific analysis revealed that spine volume was greater in primary dendrites of apical and basal segments, along with proximal segments on both apical and basal dendrites, and spine density was increased in secondary branches and distal segments on apical dendrites following sleep deprivation. Our 3D quantification suggests sleep contributes to region- and branch-specific synaptic downscaling in the hippocampus, supporting the theory of broad but selective synaptic downscaling during sleep.
越来越多的证据支持睡眠在突触可塑性和记忆巩固中的作用。一条研究路线，即突触稳态假说，强调清醒时突触强度增加，而睡眠期间（可能是较少使用的）突触进行代偿性缩小。相反，其他研究报告了睡眠剥夺后树突棘的缩小和丢失。我们想使用基因方法对树突棘进行荧光标记，以确定睡眠剥夺对海马CA1神经元树突棘的影响。雄性Vglut2-Cre小鼠在海马CA1区注射AAV-DIO-ChR2-mCherry报告基因。采用轻柔处理使小鼠从早上7点灯亮至中午12点睡眠剥夺5小时。对照小鼠和睡眠剥夺小鼠于中午12点安乐死，并进行树突棘定量分析。我们使用共聚焦显微镜成像和三维（3D）分析来量化CA1树突的细棘、蘑菇棘和短粗棘，并区分分支段。我们观察到睡眠剥夺小鼠的CA1区棘密度显著更高，主要是由于细棘数量增加，且棘体积和头部直径显著更大。分支和区域特异性分析显示，顶端和基部段的初级树突以及顶端和基部树突上的近端段的棘体积更大，睡眠剥夺后顶端树突的二级分支和远端段的棘密度增加。我们的3D定量分析表明，睡眠有助于海马体中区域和分支特异性的突触缩小，支持了睡眠期间广泛但选择性突触缩小的理论。
