Chemically specified synaptogenesis in the visual cortex

描述（改编自申请人的摘要）：长期目标是 了解视觉体验的细胞和分子机制 在生命早期到视觉皮层兴奋性突触的成熟。 皮质突触的成熟可以通过一个开关进行生物病理学检测 重复突触前动作电位引起的EPSP抑制 （不成熟）到EPSP易化（更成熟）。一般工作假设 突触后结构的分子组成与 并赋予突触前轴突成熟的程度。我们将测试 这一假设通过结合多个，突触 新生大鼠视皮层脑片内神经元的电子连接 对记录的神经元进行显微镜（EM）免疫细胞化学（ICC）分析 确定是否：（1）越成熟，促进突触表现出 NMDA受体（NMDAR）亚单位-NR 1，NR 2A-在突触后密度，以及 作为毒蕈碱乙酰胆碱能受体（mAChR）的笔突触;（2） 不成熟的、压抑的突触的特征是， 首先到达质膜，沿着到达α 7烟碱型AChR;（3）激活 这些“先锋”NMDAR调节细胞质NMDAR亚基的募集 和mAChR的新生突触后位点;（4）NMDAR的药理学阻断 将阻止NMDAR和AChR的NR 1/NR 2A异聚体的插入， 延迟或消除突触从抑制向促进的转换 表型。Aoki和Reyes的研究表明，突触的成熟度可以变化， 广泛存在于单层甚至单个神经元中。因此， 单个突触和单个突触后突触的电镜、ICC和生物物理学分析 密度应该特别有助于阐明功能联系 细胞的超微结构、分子组成和生理特性之间 出生后早期视觉皮层中形成的兴奋性突触 并决定了大脑皮层神经功能的终身能力。知识 从这样的研究中获得的是设计分子疗法所必需的， 在生命早期由于感觉剥夺而导致的缺陷。

DESCRIPTION (adapted from applicant's abstract): The long-term goal is to understand the cellular and molecular mechanisms linking visual experience during early life to maturation of excitatory synapses in the visual cortex. The maturation of cortical synapses can be detected biophysically by a switch from EPSP depression following repetitive presynaptic action potentials (immature) to EPSP facilitation (more mature). The general working hypothesis is that the molecular composition of postsynaptic structures correlates with and confers the degree of maturity upon the presynaptic axons. We will test this hypothesis by combining patch-recording of multiple, synaptically connected neurons within neonatal rat visual cortical slices with electron microscopic (EM) - immuno- cytochemical (ICC) analysis of the recorded neurons to DETERMINE WHETHER: (1) the more mature, facilitating synapses exhibit the NMDA receptor (NMDAR) subunits - NR1, NR2A - at postsynaptic densities, as well as the muscarinic acetylcholinergic receptors (mAChR) pen-synaptically; (2) the immature, depressing synapses are characterized by pioneer NMDARs that arrive to the plasma membrane first, along with alpha7 nicotinic AChR; (3) activation of these 'pioneer' NMDARs regulate recruitment of cytoplasmic NMDAR subunits and mAChRs to nascent postsynaptic sites; (4) pharmacological blockade of NMDAR will prevent the insertion of NR1/NR2A heteromers of NMDAR and AChR and also delay or abolish the switch at synapses from the depressing to the facilitating phenotype. The works of Aoki and Reyes indicate that synapse maturity can vary widely within single layers and even within single neurons. Thus, the combined EM, ICC and biophysical analysis of single synapses and single postsynaptic densities should be particularly helpful in elucidating functional links between ultrastructure, molecular composition, and physiological properties of excitatory synapses that form during early postnatal life in the visual cortex and dictate life-long capacities of cortical neural function. The knowledge gained from such a study is required in designing molecular remedies for deficits caused by sensory deprivation during early life.