Imaging Synaptic Plasticity in the Visual Cortex in Vivo

描述（由申请人提供）：本申请中提出的实验旨在研究树突棘生长和收缩在小鼠视觉皮层经验依赖可塑性中的作用。最近的证据表明，树突棘在发育和成年皮层中是动态的：每天都有新的棘出现，并向轴突生长，建立新的突触，而一些现有的棘缩回，破坏它们的突触连接。突触连通性的这些变化可能在经验依赖可塑性期间皮层回路的快速重新布线中发挥重要作用。在表达绿色荧光蛋白转基因的转基因小鼠中，脊柱生长和收缩在多大程度上影响了皮质回路的功能变化。双光子激光扫描显微镜和本征信号光学成像将在同一只小鼠单眼剥夺前后的几周内反复成像脊柱动力学和皮质眼优势功能的变化。通过对相同制备过程中结构和功能变化的成像，将有可能确定突触消除是否导致被剥夺的眼输入功能丧失，以及新的突触形成是否导致有经验的眼输入逐渐加强。体内电生理学和固定组织解剖学将用于确定在单眼剥夺后，哪些层中的哪些细胞首先改变其反应性和连通性，并绘制这些变化通过其余皮层回路的进展图。综上所述，这些实验应该提供了在感受野和突触水平上皮层结构和功能的经验依赖变化的开始和进展的详细理解。这些实验的结果可能有助于为弱视、暗斑和中风提供合理的治疗方法。

DESCRIPTION (provided by applicant): The experiments proposed in this application investigate the roles of dendritic spine growth and retraction in experience-dependent plasticity in the mouse visual cortex. Recent evidence indicates that dendritic spines are dynamic in the developing and adult cortex: new spines appear daily and grow towards axons to establish novel synapses while some existing spines retract, breaking their synaptic connection. These changes in synaptic connectivity may play important roles in rapidly rewiring cortical circuits during experience-dependent plasticity. The extent to which spine growth and retraction underlie functional changes in cortical circuits will be examined in transgenic mice expressing a green fluorescent protein transgene. 2-photon laser scanning microscopy and intrinsic signal optical imaging will used to repeatedly image spine dynamics and functional changes in cortical ocular dominance in vivo over periods of weeks in the same mice before and after monocular deprivation. By imaging changes in structure and function in the same preparation, it will be possible to determine whether synapse elimination underlies the functional loss of deprived eye inputs and novel synapse formation underlies the gradual strengthening of experienced eye inputs. In vivo electrophysiology and fixed tissue anatomy will be used to determine which cells in which layers are the first to alter their responsiveness and connectivity following monocular deprivation and to map the progression of these changes through the remainder of the cortical circuit. Taken together, these experiments should provide a detailed understanding of the onset and progression of experience-dependent changes in cortical structure and function at the level of receptive fields and synapses. Results from these experiments may aid in the provision of rationally-based therapeutic approaches to amblyopia, scotoma, and stroke.