Pain and itch are distinct sensations arousing evasion and compulsive desire for scratching, respectively. It’s unclear whether they could invoke different neural networks in the brain. Here, we use the type 1 herpes simplex virus H129 strain to trace the neural networks derived from two types of dorsal root ganglia (DRG) neurons: one kind of polymodal nociceptors containing galanin ( Gal ) and one type of pruriceptors expressing neurotensin ( Nts ). The DRG microinjection and immunosuppression were performed in transgenic mice to achieve a successful tracing from specific types of DRG neurons to the primary sensory cortex. About one-third of nuclei in the brain were labeled. More than half of them were differentially labeled in two networks. For the ascending pathways, the spinothalamic tract was absent in the network derived from Nts -expressing pruriceptors, and the two networks shared the spinobulbar projections but occupied different subnuclei. As to the motor systems, more neurons in the primary motor cortex and red nucleus of the somatic motor system participated in the Gal -containing nociceptor-derived network, while more neurons in the nucleus of the solitary tract (NST) and the dorsal motor nucleus of vagus nerve (DMX) of the emotional motor system was found in the Nts -expressing pruriceptor-derived network. Functional validation of differentially labeled nuclei by c-Fos test and chemogenetic inhibition suggested the red nucleus in facilitating the response to noxious heat and the NST/DMX in regulating the histamine-induced scratching. Thus, we reveal the organization of neural networks in a DRG neuron type-dependent manner for processing pain and itch.

中文翻译：

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源自含甘丙肽的伤害感受器和表达神经降压素的瘙痒感受器的不同神经网络

疼痛和瘙痒分别是引起逃避和强迫性抓挠欲望的截然不同的感觉。目前尚不清楚他们是否可以调用大脑中的不同神经网络。在这里，我们使用 1 型单纯疱疹病毒 H129 株来追踪源自两种背根神经节 (DRG) 神经元的神经网络：一种含有甘丙肽的多模式伤害感受器 (加仑) 和一种表达神经降压素的瘙痒感受器 (神经元). 在转基因小鼠中进行了 DRG 显微注射和免疫抑制，以实现从特定类型的 DRG 神经元到初级感觉皮层的成功追踪。大脑中大约三分之一的细胞核被标记了。其中一半以上在两个网络中被不同地标记。对于上升通路，脊髓丘脑束在源自的网络​​中不存在神经元-表达瘙痒感受器，这两个网络共享脊髓投射但占据不同的亚核。在运动系统方面，躯体运动系统的初级运动皮层和红核中的更多神经元参与了加仑-包含伤害感受器衍生网络，而在情绪运动系统的孤束核（NST）和迷走神经背侧运动核（DMX）中发现了更多的神经元神经元-表达瘙痒感受器衍生网络。通过 c-Fos 测试和化学遗传学抑制对差异标记的细胞核进行功能验证表明，红核有助于促进对有害热的反应，而 NST/DMX 可调节组胺诱导的抓挠。因此，我们以依赖于 DRG 神经元类型的方式揭示神经网络的组织以处理疼痛和瘙痒。