Synaptic Integration and Propagation in CA1 Dendrites

描述（由申请人提供）：海马CA1锥体神经元接受不同树突域的兴奋性突触输入：基底树突、顶斜树突和顶丛树突。为了了解CA1神经元如何在空间导航、学习和记忆中发挥其所提出的功能，了解这些神经元如何整合这些不同树突结构域的突触输入是至关重要的。在完整动物身上进行的实验已经确定了突触输入到不同树突区域的功能相关性，但这些输入如何整合的生物物理学仍不清楚。在这里，我们提出了一系列的研究，旨在更好地了解CA1锥体神经元整合兴奋性突触输入的细胞和分子过程。主要的方法将是利用谷氨酸的双光子释放来激活海马切片中神经元不同树突区域的树突棘。连续切片电子显微镜也将用于研究不同树突区域的树突棘和突触的结构。免疫金标记结合连续电镜技术，研究不同树突腔室中突触谷氨酸受体（AMPA和NMDA受体）、代谢型谷氨酸受体（mGluR）和乙酰胆碱受体（machr）的密度。这些突触和调节受体的功能将通过全细胞膜片钳记录和双光子释放来探索。树突整合的调节可能受mGluR和mAChR的控制，这可能解释了不同行为状态下海马的不同功能状态。结果将提供洞察突触输入的树突整合在一个前所未有的结构和分子细节水平。这些见解将有助于更好地了解海马体的功能，这对于了解影响海马体的疾病，如阿尔茨海默病、精神分裂症和癫痫，是必要的。

DESCRIPTION (provided by applicant): CA1 pyramidal neurons of the hippocampus receive excitatory synaptic input onto different dendritic domains: basal dendrites, apical oblique, and apical tuft dendrites. To understand how CA1 neurons carry out their proposed functions in spatial navigation, learning, and memory, it is critical to understand how these neurons integrate synaptic input in these different dendritic domains. Experiments in intact animals have identified functional correlates for synaptic inputs to different dendritic domains, but the biophysics of how these inputs are integrated remains unclear. Here we propose a series of studies designed to better understand the cellular and molecular processes underlying the integration excitatory synaptic inputs in CA1 pyramidal neurons. The primary approach will be to use two-photon uncaging of glutamate to activate dendritic spines in different dendritic domains of neurons in hippocampal slices. Serial-section electron microscopy will also be used to study the structure of dendritic spines and synapses in different dendritic domains. Immunogold labeling combined with serial section electron microscopy will be used to study the densities of synaptic glutamate receptors (AMPA and NMDA receptors) and metabotropic glutamate receptors (mGluR) and acetylcholine receptors (mAChRs) in different dendritic compartments. The function of these synapses and modulatory receptors will be explored using whole-cell patch-clamp recording and two-photon uncaging. Modulation of dendritic integration is likely to be under the control of mGluR and mAChR, which may account for different functional states of the hippocampus during different behavioral states. The results will offer insight into dendritic integration of synaptic inputs at an unprecedented level of structural and molecular detail. Such insights will lead to a better understanding of hippocampal function, which is necessary to understand diseases affecting the hippocampus, such as Alzheimer's disease, schizophrenia, and epilepsy. PUBLIC HEALTH RELEVANCE: We will use, whole-cell patch-clamp recording in hippocampal slices, two-photon uncaging of glutamate, pharmacology, and electron microscopy to study the role of voltage-gated channels in synaptic integration in the dendrites of CA1 neurons. We will determine the mechanisms of integration in four dendritic domains, as well as their modulation by glutamate and acetylcholine. CA1 neurons are among the most abundant in the hippocampus, and they are affected in diseases such as epilepsy and Alzheimer's disease.