Chronic itch by neuron–glia interactions in the spinal dorsal horn

Itch sensation is a defense system that responds rapidly to a wide range of harmful internal and external stimuli. Recent progress in our understanding of the neuronal basis for itch sensation in the nervous systems has been made, but the mechanism underly ing how itch turns into a pathological chronic state, such as atopic dermatitis, remains poorly understood. It is becoming clear that chronic itch is not simply a con-sequence of the continuity of acute itch signals, but rather of maladaptive function in the nervous system that is caused by long–term structural and functional alterations following skin inflammation. Recent studies have uncovered the causal role of glial cells in the spinal dorsal horn using mouse models of chronic itch including atopic dermatitis. Understanding the key roles of neuron–glia interactions may provide us with exciting insights into the mechanisms for the chronicity of itch and clues to develop novel therapeutic agents for treating chronic itch.