Neural processing of itch

Abstract

While considerable effort has been made to investigate the neural mechanisms of pain, much less effort has been devoted to itch, at least until recently. However, itch is now gaining increasing recognition as a widespread and costly medical and socioeconomic issue. This is accompanied by increasing interest in the underlying neural mechanisms of itch, which has become a vibrant and rapidly-advancing field of research. The goal of the present forefront review is to describe the recent progress that has been made in our understanding of itch mechanisms.

Functional magnetic resonance imaging in dermatology: The skin, the brain and the invisible

“…[73,74] The peripheral pathophysiology of itch is highly complex and cannot be adequately covered here; however, the following references provide a comprehensive overview. [55,[74][75][76][77] In the reviewed fMRI studies, numerous cutaneous itch models perceived itch qualities and response to antipruritic treatments. [75,78,79] C-fibres transmit itch signals to secondary neurons in the dorsal horn, from where they ascend in the contralateral spinothalamic tract to the thalamus, which distributes the signals to the itch-processing brain structures.…”

Le prurit : des avancées physiopathologiques considérables

“…L'histamine est loin d'être le seul médiateur impliqué dans le prurit [10]. Elle peut même ne pas intervenir du tout dans certains prurits.…”

“…De même, des preuves claires attestent de l'existence d'une voie indépendante de l'histamine, dépendante de l'activation périphérique de PAR-2, et située dans le tractus spinothalamique [23]. Les deux sous-ensembles sont mutuellement exclusifs [10]. Une voie dépendante du GRP (gastrin-releasing peptide) a été aussi mise en évidence [24], ses liens avec les deux voies précé-dentes restant à déterminer.…”

Molecular Mechanisms of Itch and Pain: An Overview

“…Itch is defined as an "unpleasant sensation that elicits the desire to scratch," and pain is an "unpleasant sensory and emotional experience associated with actual or potential tissue damage" [1] . Although their definitions are distinct, they share many similarities.…”

“…As obvious in their definition, pain elicits a withdrawal response while itch elicits a scratch response. In addition, unlike a pain sensation, an itch sensation is perceived only at the body surface [1] . What is more interesting is that itch and pain often counter-regulate each other.…”