title: Sex differences in itch perception and modulation by distraction--an FMRI pilot study in healthy volunteers.
abstract: BACKGROUND
  Even though itch is a common syndrome of many diseases there is only little knowledge about sex and gender differences in pruritus, especially in central itch perception and modulation. To our knowledge, this is the first fMRI study examining sex differences in perception and its modulation by distraction.
  
  
  METHODS
  Experimental itch was induced by application of histamine (0.1 mM) via microdialysis fibers twice at the left forearm and twice at the left lower leg in 33 healthy volunteers (17 females, 16 males). The brain activation patterns were assessed by fMRI during itch without and with distraction (Stroop task). Between the various conditions, subjects were asked to rate itch intensity, desire to scratch and pain intensity. In a second experiment in 10 of the 33 volunteers histamine was replaced by saline solution to serve as control for the 'Stroop' condition.
  
  
  RESULTS
  Women generally presented higher itch intensities compared to men during itch over the course of the experiment. A more specific analysis revealed higher itch intensities and desire to scratch in women during experimental induced itch that can be reduced by distraction at the lower legs when itch is followed by 'Stroop'. In contrast, men depicted significant reduction of 'itch' by 'Stroop' at the forearms. Women depicted higher brain activation of structures responsible for integration of sensory, affective information and motor integration/planning during 'itch' and 'Stroop' condition when compared to men. No sex differences were seen in the saline control condition.
  
  
  CONCLUSIONS
  Women and men exhibited localisation dependent differences in their itch perception with women presenting higher itch intensities and desire to scratch. Our findings parallel clinical observations of women reporting higher itch intensities depending on itch localisation and suffering more from itch as compared to men.
authors.affiliation: Department of Psychosomatics and Psychotherapy, University of Muenster, Muenster, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Stumpf
authors.forename: Markus
authors.initials: M
authors.lastname: Burgmer
authors.forename: Gudrun
authors.initials: G
authors.lastname: Schneider
authors.forename: Gereon
authors.initials: G
authors.lastname: Heuft
authors.forename: Martin
authors.initials: M
authors.lastname: Schmelz
authors.forename: Ngoc Quan
authors.initials: NQ
authors.lastname: Phan
authors.forename: Sonja
authors.initials: S
authors.lastname: Ständer
authors.forename: Bettina
authors.initials: B
authors.lastname: Pfleiderer
mesh_terms: D000328:Adult; D005260:Female; D006632:Histamine / Q000008:administration & dosage / Q000009:adverse effects*; D017442:Histamine Agonists / Q000008:administration & dosage / Q000009:adverse effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010465:Perception / Q000187:drug effects*; D010865:Pilot Projects; D011537:Pruritus / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000503:physiopathology; D011859:Radiography; D012727:Sex Characteristics
chemical_list: D017442:Histamine Agonists; D006632:Histamine