Effects of Tyr-MIF's family of peptides on immobilization stress-induced antinociception in rats.
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.
Bocheva
Adriana I
AI
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Dzambazova-Maximova
Elena B
EB
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
C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone