Progress has been made in the study of itch-control mechanisms.

On December 5, the Journal of the National Academy of Sciences published a research paper entitled "regulation of GRPR positive neurons in the spinal cord by local and long-term inhibitory projections".the study was completed by sun Yangang, the National Key Laboratory of neuroscience and the center for excellence and innovation of brain science and intelligent technology, Chinese Academy of Sciences.itching is a kind of body sensation different from pain, temperature and touch, which can induce conservative scratching behavior in human and other animals.however, for patients with chronic itching, persistent scratching caused by itching can lead to skin damage, infection and abnormal pain.in order to relieve the pain caused by chronic itching fundamentally, it is necessary to deeply understand the neural mechanism of itch signal processing and regulation.neurons expressing gastrin releasing peptide receptor (GRPR +) in the dorsal horn of the spinal cord play an important role in itching signal processing, but how these neurons are regulated by the local spinal cord and long-term inhibitory loops of the medulla oblongata is unknown.in combination with photogenetics and patch clamp electrophysiological recording, the research team found that galanin + neurons, a subgroup of inhibitory interneurons in the spinal dorsal horn, formed inhibitory synaptic connections with GRPR + neurons in the spinal dorsal horn, and played a key role in the gating of GRPR + neuron dependent itching signal transmission.activation of galanin + neurons in the dorsal horn of spinal cord of mice can inhibit the scratching behavior induced by various itching agents, but not affect the pain perception behavior of mice; killing these neurons can enhance the scratching behavior induced by itching agents.in addition, GRPR + neurons in the spinal cord also received inhibitory inputs from rostral ventromedial medulla (RVM) and serotonin inputs.therefore, both local inhibition loop and long-term inhibitory projection can directly regulate the activity of GRPR + neurons, thereby gating the processing of itching signals at the spinal level.this study has deeply analyzed the gating mechanism of local spinal and medullary long-range circuits on itch signaling pathway.the research was directed by researcher sun Yangang. Doctoral students Liu Mingzhe and Chen Xiaojun were the co first authors of the paper. At the same time, Liang Tongyu, Wang Meng, Zhang Xinyan and Li Qing of the research group also made important contributions, and were greatly assisted by researcher sun Qiang and assistant researcher Li Yuzhuo.confocal imaging, fluorescence microscopy imaging and other related work were completed in the optical imaging platform of brain intelligence Excellence Center. Hu Qian, Xiang Dan, Chen Xuxin, Wang Yonghong and Zhang Yumei provided help in data acquisition and analysis.the work has been supported by NSFC and Shanghai major projects.the GRPR + neurons in the spinal cord are regulated by local and long-range loops.GRPR + neurons in the dorsal horn of the spinal cord received inhibitory projections from galanin + and GABAergic neurons in the RVM.killing galanin + neurons in the dorsal horn of spinal cord, the gating effect of itch signaling pathway was destroyed and itching behavior was increased in mice. RVM: rostral ventromedial medulla oblongata, 5-HT: 5-HT, GRPR: gastrin releasing peptide receptor. source: brain science and intelligent technology innovation center of Chinese Academy of Sciences