Chemically specified synaptogenesis in the visual cortex

描述(摘自申请者的摘要)：长期目标是了解细胞和分子机制与视觉体验的联系 从生命早期到视皮层兴奋性突触的成熟。 大脑皮层突触的成熟可以通过一个开关来检测 重复突触前动作电位后的EPSP抑制 (不成熟)到EPSP易化(更成熟)。一般工作假说 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 这一假说是通过结合多个突触的斑块记录 新生大鼠视皮层脑片内神经元的电子连接 记录神经元的显微(EM)-免疫细胞化学(ICC)分析 为了确定：(1)更成熟、更容易的突触是否表现出 NMDA受体(NMDAR)亚单位-NR1、NR2A-也在突触后密度 作为M胆碱能受体(MAChR)的笔状突触； 不成熟、令人沮丧的突触的特征是先驱NMDAR 首先与α7烟碱AChR一起进入质膜；(3)激活 这些先驱NMDAR调节细胞质NMDAR亚单位的招募 和mAChRs到新生的突触后部位；(4)药物阻断NMDAR 会阻止NMDAR和AChR的NR1/NR2A异构体的插入，还 延迟或取消突触从抑制到促进的转换 表型。青木和雷耶斯的研究表明，突触的成熟度可以有所不同 广泛存在于单层，甚至单个神经元内。因此，合并后的 单个突触和单个突触后的EM、ICC和生物物理分析 密度在阐明功能连接方面应该特别有用 在超微结构、分子组成和生理特性之间的关系 视皮质中在出生后早期形成的兴奋性突触 并决定了皮质神经功能的终生能力。《知识》 从这样的研究中获得的结果是设计分子疗法所必需的 在生命早期由于感觉丧失而导致的缺陷。

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.