Imaging Synaptic Plasticity in the Visual Cortex in Vivo

描述(申请人提供)：本申请中提出的实验调查树突生长和回缩在小鼠视皮层经验依赖性可塑性中的作用。最近的证据表明，树突棘在发育中的和成年的皮质中是动态的：新的刺每天都会出现，并朝向轴突生长以建立新的突触，而一些现有的刺缩回，破坏它们的突触连接。突触连接的这些变化可能在经验依赖性可塑性过程中快速重新连接皮质回路方面发挥重要作用。在表达绿色荧光蛋白转基因的转基因小鼠中，将检测脊椎生长和回缩在多大程度上导致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被用来重复成像同一小鼠在单眼剥夺前后几周内体内皮质眼优势的脊柱动力学和功能变化。通过对同一制剂中结构和功能的变化进行成像，将有可能确定突触的消除是否导致剥夺的眼睛输入的功能丧失，而新的突触形成是经验的眼睛输入逐渐加强的基础。在体内，电生理学和固定组织解剖学将被用来确定在单眼剥夺后，哪些层中的哪些细胞最先改变其反应性和连接性，并通过皮质回路的其余部分绘制这些变化的进展图。综上所述，这些实验应该可以在感受野和突触水平上详细了解大脑皮质结构和功能的经验依赖性变化的发生和发展。这些实验的结果可能有助于为弱视、暗点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.