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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。
Objective To observe the distribution of the itch-specific Mrgpr A3 + neurons in the dorsal root ganglion (DRG) of mice. METHODS: Mrgpr A3 + neurons were labeled with EGFP and td Tomato by genetic method. Three homozygous Mrgpra3EGFP-Cre and ROSA26td Tomato adult transgenic mice were selected and the skin and dorsal root ganglion were isolated. Laser scanning confocal imaging technique was used to observe the projection distribution of peripheral nerve fibers of Mrgpr A3 + neurons in the somatic skin of mice. The three-dimensional spatial distribution of Mrgpr A3 + neurons in the whole dorsal root ganglion was observed by two-photon imaging. Results The Mrgpr A3 + nerve fibers on the cheek, back and foot skin were densely distributed, coarse and long, and distributed widely. The Mrgpr A3 + nerve fibers on the skin of neck and abdomen were sparse, short and small, scattered in spots. Mrgpr A3 + The hairy and glabrous areas of the skin both have projection distribution, and the distribution characteristics of different parts are different. Almost all Mrgpr A3 + neurons are small diameter sensory neurons, and in the cervical, thoracic, lumbar and caudal dorsal root ganglia The Z-axis imaging depths of the cervical, thoracic, lumbar and caudal segments were 350μm, 250μm, 400μm and 200μm, respectively. The three-dimensional spatial distribution of Mrgpr A3 + neurons in different parts of the somatic body was in different sections There are significant differences between the segments. Conclusion The distribution of Mrgpr A3 + nerve fibers in different parts of the body of the mice is different from that of Mrgpr A3 + neurons in the whole dorsal root ganglion. The differences in the distribution of the neurons and the terminals of the itch may be in different regions There is a structural basis of differences in the physiological response to itchiness.