title: Interleukin-2-induced antinociception in morphine-insensitive rats.
abstract: OBJECTIVE
  To investigate interleukin-2-induced antinociception in morphine-insensitive rats.
  
  
  METHODS
  Paw withdrawal latencies (PWL) to noxious radiant heat were taken as the measurement of pain threshold.
  
  
  RESULTS
  Intraplantar injection of human recombinant interleukin-2 (1.5 x10(4) U) significantly increased PWL in normal rats. PWL was also markedly increased by IL-2 in 45-d-post-complete Freund's adjuvant (CFA)-treated rats, which have been proven morphine-insensitive. IL-2-induced antinociception in CFA-treated rats were significantly lower than that in normal rats. IL-2-induced antinociception was partially blocked by naloxone (1 mg/kg, ip) in normal rats but remained unchanged in CFA group.
  
  
  CONCLUSIONS
  IL-2-induced antinociception is partially mediated by mu-opioid receptors. Therapeutic applications of IL-2 may also be expanded to relieve morphine-insensitive pain.
authors.affiliation: Institute of Neurobiology, Fudan University, Shanghai 200433, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Song
authors.forename: Xin-Yuan
authors.initials: XY
authors.lastname: Liu
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Zhao
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D004361:Drug Tolerance; D005620:Freund's Adjuvant / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D009020:Morphine / Q000009:adverse effects*; D009270:Naloxone / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy; D017288:Pain Threshold / Q000187:drug effects*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000700:Analgesics; D007376:Interleukin-2; D017450:Receptors, Opioid, mu; D011994:Recombinant Proteins; D009270:Naloxone; D009020:Morphine; D005620:Freund's Adjuvant