title: Effects of Tyr-MIF's family of peptides on immobilization stress-induced antinociception in rats.
abstract: The Tyr-MIF-1 family of peptides includes MIF-1, Tyr-MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1, which have been isolated from bovine hypothalamus and cortex of human brain. Data in the literature suggest that peptides of Tyr-MIF-1's family have opioid-like and anti-opioid actions. All these peptides interact with opioid receptors and in addition bind to non-opiate sites specific for each of the peptides and able to inhibit the expression of some forms of stress-induced analgesia (SIA) in various species.
  
  
  OBJECTIVE
  To examined the effects of the Tyr-MIF-1's peptides on immobilization stress-induced antinociception.
  
  
  METHODS
  Tyr-MIF-1's peptides were given to male Wistar rats intraperitoneally before or after 1 hour of restraint. The changes in the mechanical nociceptive threshold of the animals were measured by the Randall-Selitto paw pressure test.
  
  
  RESULTS
  Immobilization of the rats increased the pain threshold at least 1 h. Tyr-MIF-1's peptides have contrasting effects on immobilization stress-induced antinociception in paw-pressure test in rats. When administered before immobilization procedure they potentiated the immobilization stress-induced antinociception, while if given after immobilization, they reduced it. Antinociceptive effects of Tyr-MIF-1, Tyr-W-MIF-1 and Tyr-K-MIF-1 were reduced in condition of stress.
  
  
  CONCLUSIONS
  Tyr-MIF-1's peptides exerted antiopioide effects under condition of stress in paw-pressure test. These antiopioide effects were more pronounced when peptides were injected after stress exposure.
authors.affiliation: Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
authors.forename: Adriana I
authors.initials: AI
authors.lastname: Bocheva
authors.forename: Elena B
authors.initials: EB
authors.lastname: Dzambazova-Maximova
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D007103:Immobilization; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008297:Male; D009619:Nociceptors / Q000187:drug effects*; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar
chemical_list: C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone