Structural Basis for Noradrenergic Regulation of Neural Circuits in the Mouse Olfactory Bulb
Structural Basis for Noradrenergic Regulation of Neural Circuits in the Mouse Olfactory Bulb
复制标题
小鼠嗅球神经回路去甲肾上腺素能调节的结构基础
DOI：
10.1002/cne.25085
复制
发表时间：
2021
影响因子：
2.5
通讯作者：
Toida K.
中科院分区：
文献类型：
--
作者：
Horie S.;Kiyokage E.;Hayashi S.;Inoue K.;Sohn J.;Hioki H.;Furuta T.;Toida K.
嗅觉输入在主嗅球（OB）的肾小球中进行处理，并通过投射神经元传递到大脑的更高中心。相反，来自其他大脑区域的离心输入投射到OB。我们之前使用单个神经元标记分析了来自多个大脑区域的离心输入到OB。在这项研究中，我们分析了来自蓝斑（LC）的离心去甲肾上腺素能（NA）纤维，因为它们在OB中的投射途径和突触连接尚未得到详细的阐明。我们通过单神经元标记和免疫电镜分析NA离心投影。使用Neurolucida软件对被病毒感染标记的单个NA神经元进行三维追踪，以可视化从LC到OB的投射途径。此外，使用去甲肾上腺素转运蛋白（NET）抗体可视化离心NA纤维。NET免疫反应性（- ir）纤维含有许多静脉曲张和突触囊泡。此外，电子断层扫描表明，NET - ir纤维形成了不同形态的不对称突触。尽管这些突触以静脉曲张形式存在，但整个OB区的突触密度相对较低。突触密度最大的是外丛状层；在所有观察到的静脉曲张中，约有17%含有突触。这些结果强烈表明，OB中含有NA的纤维从静脉曲张和突触释放NA，从而影响OB神经元的活动。本研究为从LC中提取的离心NA纤维进行嗅觉调节提供了形态学基础。
Olfactory input is processed in the glomerulus of the main olfactory bulb (OB) and relayed to higher centers in the brain by projection neurons. Conversely, centrifugal inputs from other brain regions project to the OB. We have previously analyzed centrifugal inputs into the OB from several brain regions using single‐neuron labeling. In this study, we analyzed the centrifugal noradrenergic (NA) fibers derived from the locus coeruleus (LC), because their projection pathways and synaptic connections in the OB have not been clarified in detail. We analyzed the NA centrifugal projections by single‐neuron labeling and immunoelectron microscopy. Individual NA neurons labeled by viral infection were three‐dimensionally traced using Neurolucida software to visualize the projection pathway from the LC to the OB. Also, centrifugal NA fibers were visualized using an antibody for noradrenaline transporter (NET). NET immunoreactive (‐ir) fibers contained many varicosities and synaptic vesicles. Furthermore, electron tomography demonstrated that NET‐ir fibers formed asymmetrical synapses of varied morphology. Although these synapses were present at varicosities, the density of synapses was relatively low throughout the OB. The maximal density of synapses was found in the external plexiform layer; about 17% of all observed varicosities contained synapses. These results strongly suggest that NA‐containing fibers in the OB release NA from both varicosities and synapses to influence the activities of OB neurons. The present study provides a morphological basis for olfactory modulation by centrifugal NA fibers derived from the LC.