title: Anatomy and neurophysiology of pruritus.
abstract: Itch has been described for many years as an unpleasant sensation that evokes the urgent desire to scratch. Studies of the neurobiology, neurophysiology, and cellular biology of itch have gradually been clarifying the mechanism of itch both peripherally and centrally. The discussion has been focused on which nerves and neuroreceptors play major roles in itch induction. The "intensity theory" hypothesizes that signal transduction on the same nerves leads to either pain (high intensity) or itch (low intensity), depending on the signal intensity. The "labeled-line coding theory" hypothesizes the complete separation of pain and itch pathways. Itch sensitization must also be considered in discussions of itch. This review highlights anatomical and functional properties of itch pathways and their relation to understanding itch perception and pruritic diseases.
authors.affiliation: Department of Dermatology and Surgery, University of California, San Francisco, San Francisco, CA, USA. IkomaA@derm.ucsf.edu
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ikoma
authors.forename: Ferda
authors.initials: F
authors.lastname: Cevikbas
authors.forename: Cordula
authors.initials: C
authors.lastname: Kempkes
authors.forename: Martin
authors.initials: M
authors.lastname: Steinhoff
mesh_terms: D000344:Afferent Pathways / Q000502:physiology / Q000503:physiopathology*; D000818:Animals; D001921:Brain / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D011537:Pruritus / Q000503:physiopathology*; D011984:Sensory Receptor Cells / Q000502:physiology*; D012867:Skin / Q000294:innervation / Q000503:physiopathology*; D013116:Spinal Cord / Q000502:physiology / Q000503:physiopathology