title: Visceral pain perception is determined by the duration of colitis and associated neuropeptide expression in the mouse.
abstract: BACKGROUND
  Even though inflammation is a traditional tool for the induction of hyperalgesia in many tissues, recent observations suggest that not all inflammatory processes produce this change. Tolerance to colorectal distension (CRD) is reduced in patients with acute ulcerative colitis but is increased in patients with chronic inflammatory bowel disease. This suggests that the nature of the inflammatory infiltrate influences visceral perception.
  
  
  OBJECTIVE
  To test this hypothesis by assessing responses to CRD in mice with mild, acute or chronic colitis.
  
  
  METHODS
  CRD responses were measured in mice with mild non-specific colitis, and dextran sodium sulphate (DSS)-induced acute and chronic colitis. Responses were compared with tissue infiltrate and damage, interleukin (IL)1beta and myeloperoxidase (MPO) activity and substance P, beta-endorphin and micro opioid receptor (MOR) expression.
  
  
  RESULTS
  Mild and acute colitis were associated with increased responsiveness to CRD. In contrast, CRD responses were not increased in mice with chronic colitis and this difference was not due to altered colonic wall compliance. MPO and IL1beta levels were greater in acute than in chronic colitis. Larger increases in tissue substance P were seen in acute than in chronic DSS, whereas CD4 T cells, beta-endorphin and MOR expression were evident only in chronic colitis. An inverse correlation was seen between substance P and MOR in these tissues.
  
  
  CONCLUSIONS
  Acute colitis increased responsiveness to CRD and is accompanied by an acute inflammatory infiltrate and increased tissue substance P. Chronic DSS is accompanied by an increase in beta-endorphin and MOR expression, and CD4 T cells, but no change in compliance or CRD responses. We conclude that acute inflammation generates hyperalgesia, whereas chronic inflammation involves infiltration by lymphocytes accompanied by MOR and beta-endorphin up regulation, and this provides an antinociceptive input that restores normal visceral perception.
authors.affiliation: Intestinal Disease Research Programme, McMaster University, Health Sciences Bldg, Hamilton, ON, Canada. vermam@mcmaster.ca
authors.forename: Monica
authors.initials: M
authors.lastname: Verma-Gandhu
authors.forename: Elena F
authors.initials: EF
authors.lastname: Verdu
authors.forename: Premysl
authors.initials: P
authors.lastname: Bercik
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Blennerhassett
authors.forename: Nafia
authors.initials: N
authors.lastname: Al-Mutawaly
authors.forename: Jean-Eric
authors.initials: JE
authors.lastname: Ghia
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Collins
mesh_terms: D000208:Acute Disease; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002908:Chronic Disease; D003092:Colitis / Q000150:complications* / Q000276:immunology / Q000378:metabolism; D003106:Colon / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D003187:Compliance; D053583:Interleukin-1beta / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009479:Neuropeptides / Q000378:metabolism*; D010146:Pain / Q000209:etiology* / Q000276:immunology / Q000378:metabolism; D017288:Pain Threshold; D010812:Physical Stimulation / Q000379:methods; D017450:Receptors, Opioid, mu / Q000378:metabolism; D013373:Substance P / Q000378:metabolism; D001615:beta-Endorphin / Q000378:metabolism
chemical_list: D053583:Interleukin-1beta; D009479:Neuropeptides; D017450:Receptors, Opioid, mu; D013373:Substance P; D001615:beta-Endorphin