Identification of a Spinal Circuit for Mechanical and Persistent Spontaneous Itch

Publication date: Available online 16 July 2019Source: NeuronAuthor(s): Haili Pan, Mahar Fatima, Alan Li, Hankyu Lee, Wei Cai, Lorraine Horwitz, Chia Chun Hor, Nizam Zaher, Mitchell Cin, Hannah Slade, Tianwen Huang, X.Z. Shawn Xu, Bo DuanSummaryLightly stroking the lips or gently poking some skin regions can evoke mechanical itch in healthy human subjects. Sensitization of mechanical itch and persistent spontaneous itch are intractable symptoms in chronic itch patients. However, the underlying neural circuits are not well defined. We identified a subpopulation of excitatory interneurons expressing Urocortin 3::Cre (Ucn3+) in the dorsal spinal cord as a central node in the pathway that transmits acute mechanical itch and mechanical itch sensitization as well as persistent spontaneous itch under chronic itch conditions. This population receives peripheral inputs from Toll-like receptor 5-positive (TLR5+) Aβ low-threshold mechanoreceptors and is directly innervated by inhibitory interneurons expressing neuropeptide Y::Cre (NPY+) in the dorsal spinal cord. Reduced synaptic inhibition and increased intrinsic excitability of Ucn3+ neurons lead to chronic itch sensitization. Our study sheds new light on the neural basis of chronic itch and unveils novel avenues for developing mechanism-specific therapeutic advancements.Graphical Abstract

Source: Neuron - July 18, 2019 Category: Neuroscience Source Type: research