小鼠背根神经节中痒觉神经元的分布特性

目的观察小鼠背根神经节(DRG)中痒觉特异性Mrgpr A3+神经元的分布特征。方法采用遗传学方法将Mrgpr A3+神经元特异性标记强化绿色荧光蛋白(EGFP)和td Tomato;选取3只纯合Mrgpra3EGFP-Cre;ROSA26td Tomato成年转基因小鼠,分离皮肤和背根神经节组织;采用激光扫描共焦成像技术观察Mrgpr A3+神经元的外周神经纤维在小鼠躯体皮肤的投射分布特征;采用双光子成像技术观察Mrgpr A3+神经元在整体背根神经节中的三维空间分布情况。结果脸颊、背部和脚掌皮肤的Mrgpr A3+神经纤维分布密集,粗且长,分布广泛;颈部和腹部皮肤的Mrgpr A3+神经纤维分布稀疏,短且小,呈散点状分布;Mrgpr A3+神经纤维在皮肤的有毛和无毛区域都有投射分布,且不同部位分布特点不同;几乎所有的Mrgpr A3+神经元都为小直径感觉神经元,且在颈、胸、腰、尾段背根神经节中均有分布;颈段、胸段、腰段和尾段的Z轴成像深度分别为350μm、250μm、400μm和200μm;躯体不同部位背根神经节中的Mrgpr A3+神经元的三维空间分布在不同节段存在明显差异。结论小鼠躯体不同部位皮肤的Mrgpr A3+神经纤维的分布特征和整体背根神经节中Mrgpr A3+神经元的三维空间分布特征都存在较大差异,痒觉神经元和末梢分布的差异可能是不同区域存在痒觉生理反应差异的结构基础。

Distribution features of itch-specific neurons in dorsal root ganglion in mice

Objective To observe the distribution features of itch-specific MrgprA3⁺neurons located in the dorsal root ganglion (DRG).Methods The MrgprA3⁺neurons were specifically labeled by enhaced green fluorescence protein(EGPF) and tdTomato using a genetic method. The skin and DRG tissues in the 3 adult homogenous transgenic Mrgpra3 ^EGFP-Cre ;ROSA26 ^tdTomato mice were collected. The peripheral MrgprA3⁺fibers innervating the skin were imaged by using confocal imaging technology. The distribution of MrgprA3⁺neurons in the intact DRG tissue was observed using two-photo imaging technology.Results The MrgprA3⁺fibers in cheek, back and paw skins were densely and widely distributed with clearly coarse and long features. By contrast, the MrgprA3⁺fibers in neck and abdomen skins were sparsely distributed with short and dotted features. The MrgprA3⁺fibers were distributed in both hairy and glabrous skins and showed different properties in various parts of body. Almost all of MrgprA3⁺neurons belonged to small diameter sensory neurons and located in the cervical, thoracic, lumbar and sacral DRG tissues. The Z axis imaging depth was 350μm in cervical DRG, 250μm in thoracic DRG, 400μm in lumbar DRG and 200μm in sacral DRG. Three dimensional spatial distributions of MrgprA3⁺neurons in various DRG tissues had significant differences.Conclusion The MrgprA3⁺fibers in various peripheral skin and MrgprA3⁺neurons located in intact DRG tissues show different distribution properties. The differences in the distribution of itch neurons and terminals may be the structural basis for the differences in the presence of itch sensation in different areas.