Heterogeneous properties of LC efferents to modality-specific terminal fields

描述(申请人提供)：本项目的主要目标是确定支配大鼠前额叶和运动皮质各亚区的蓝斑(LC)神经元的解剖组织、分子表型和电生理特性。前额叶皮质(PFC)包括其子区域眶前叶皮质(OFC)、内侧前额叶 大脑皮质(MPFC)、前扣带回皮质(ACC)和初级运动皮质(M1)均由LC支配，并受其初级递质去甲肾上腺素(NE)的调节作用。每个PFC亚区调节执行功能的不同方面，这些功能在许多神经精神疾病中受到损害，包括ADHD、PTSD和精神分裂症。同样，NE系统也参与了许多依赖PFC的行为功能的控制，包括灵活和持续的注意。这项拟议研究的第一个目标将包括逆行追踪研究和免疫组织化学程序，以识别和表征LC内投射到每个PFC亚区的含NE神经元的亚群。在这个和所有随后的目标中，M1将作为一个非认知性大脑区域进行比较。该项目的第二个目标将通过结合激光显微解剖、RNA微阵列分析和qRT-PCR检查每类投射细胞的转录和对去甲肾上腺素功能至关重要的选定基因的表达水平，来确定每类投射细胞的分子组成。第三个目标是使用全细胞膜片钳技术，根据膜特性、突触反应和对药物激活的敏感性来分析单个LC-PFC和M1投射细胞。这些研究将对LC-皮质投射的解剖、分子和生理属性提供更全面的了解，并挑战长期以来的观点，即LC是含有NE的神经元的功能同质簇，同时在所有LC-去甲肾上腺素能终末区域施加统一的调制效应。相反，一般的工作假设是LC-NE系统通过对特定于通道的终端场的异质和异步调制来操作。这一新的理论构建对我们理解正常的大脑功能和治疗许多神经精神疾病具有深远的意义，这些疾病包括去甲肾上腺素和前额叶皮质功能障碍。

DESCRIPTION (provided by applicant): The primary goal of this project is to determine the anatomical organization, molecular phenotype, and electrophysiological properties of locus coeruleus (LC) neurons that innervate sub-regions of the rat prefrontal and motor cortex. The prefrontal cortex (PFC) including its sub-regions the orbitofrontal cortex (OFC), medial prefrontal cortex (mPFC), and anterior cingulate cortex (ACC), and the primary motor cortex (M1) are innervated by the LC and subject to the modulatory actions of its primary transmitter, norepinephrine (NE). Each of the PFC sub-regions mediates distinct aspects of executive function that are compromised in many neuropsychiatric disorders including ADHD, PTSD, and schizophrenia. Likewise, the NE system has been implicated in the control of many PFC-dependent behavioral functions including flexible and sustained attention. The first aim of the proposed research will include retrograde tracing studies and immunohistochemical procedures to identify and characterize the subsets of NE-containing neurons within the LC that project to each PFC sub-region. In this and all subsequent aims M1 will serve as a non-cognitive brain region for comparison. The second aim of the project will determine the molecular complement of each class of projection cells by examining their transcriptomes and their expression levels of selected genes that are critical for noradrenergic function using combinations of laser micro-dissection, RNA microarray analysis and qRT-PCR. The third aim will profile individual LC-PFC and M1 projection cells on the basis of membrane properties, synaptic responsiveness, and sensitivity to drug activation using whole cell patch clamp techniques. These studies will provide a more complete understanding of the anatomical, molecular, and physiological attributes of the LC-cortical projection and challenge the longstanding notion that the LC is a functionally homogeneous cluster of NE-containing neurons that exert uniform modulatory effects across all LC- noradrenergic terminal fields, simultaneously. Instead, the general working hypothesis is that the LC-NE system operates by heterogeneous and asynchronous modulation of modality-specific terminal fields. This new theoretical construct has far reaching implications for our understanding of normal brain function and treatment of many neuropsychiatric disorders that involve noradrenergic and prefrontal cortical dysfunction.