Spinal Neuropeptide Y1 Receptor-Expressing Neurons Form an Essential Excitatory Pathway for Mechanical Itch

Abstract

Summary: Acute itch can be generated by either chemical or mechanical stimuli, which activate separate pathways in the periphery and spinal cord. While substantial progress has been made in mapping the transmission pathway for chemical itch, the central pathway for mechanical itch remains obscure. Using complementary genetic and pharmacological manipulations, we show that excitatory neurons marked by the expression of the neuropeptide Y1 receptor (Y1Cre neurons) form an essential pathway in the dorsal spinal cord for the transmission of mechanical but not chemical itch. Ablating or silencing the Y1Cre neurons abrogates mechanical itch, while chemogenetic activation induces scratching. Moreover, using Y1 conditional knockout mice, we demonstrate that endogenous neuropeptide Y (NPY) acts via dorsal-horn Y1-expressing neurons to suppress light punctate touch and mechanical itch stimuli. NPY-Y1 signaling thus regulates the transmission of innocuous tactile information by establishing biologically relevant thresholds for touch discrimination and mechanical itch reflexes. : Acton et al. identify the excitatory neurons in the dorsal spinal cord that drive mechanical itch. These cells mediate responses to light punctate touch and are inhibited by neuropeptide Y (NPY)::Cre interneurons. Light touch sensitivity and mechanical itch responses are gated by NPY signaling mediated by Y1-expressing neurons in the dorsal horn. Keywords: mechanical itch transmission, touch, dorsal spinal cord, Y1 excitatory neurons, inhibition, neuropeptide Y, NPY1R signaling, somatosensory processing, chemical itch, pain