Inhibitory influences of MIF-1 (PLG) and Tyr-MIF-1 (YPLG) on aggression and defeat-induced analgesia in mice

The effects of prolyl-leucyl-glycinamide (MIF-1, PLG), tyrosine-prolyl-leucyl-glycinamide (Tyr-MIF-1, YPLG) and the exogenous opiate antagonist, naloxone, on aggressive interactions and defeat-induced analgesia were examined in male mice. All three substances reduced the number of bites required to obtain defeat in subordinate mice during aggressive encounters, as well as blocking subsequent defeat-induced analgesia. Tyr-MIF-1 had significantly greater inhibitory effects than MIF. These results suggest that both MIF and Tyr-MIF-1 may function as endogenous opioid antagonists and have inhibitory influences on aggression, with the antagonistic effects of Tyr-MIF-1 being more potent than those of MIF-1.     

Prolyl-leucyl-glycinamide reduces aggression and blocks defeat-induced opioid analgesia in mice

The effects of Prolyl-leucyl-glycinamide (PLG, MIF-1) and the exogenous opiate antagonist naloxone, on aggressive interactions and defeat-induced analgesia were examined in male mice. Both substances reduced the number of bites required to obtain defeat in subordinate mice during aggressive encounters as well as blocking the subsequent defeat-induced analgesia. These results suggest that MIF-1 may function as an endogenous opioid antagonist and have an inhibitory influence on aggression.     

The effect of oxytocin and fragment (MIF-I) on the development of tolerance to hypothermic and hypnotic action of ethanol in the rat

The daily pretreatment of rats with oxytocin (OXY) or MIF-I prior to ethanol (Et-OH) administration markedly altered the alcohol tolerance when tested on the fifth day of treatment. OXY (800 and 2400 nmole/kg SC) and MIF (800 nmole/kg SC) inhibited the development of tolerance to the hypnotic effect of Et-OH. MIF at this dose also inhibited the tolerance to the hypothermic effect. Only OXY in the dose of 800 nmole/kg suppressed hypothermia in an acute experiment with Et-OH and produced by itself hypothermia after acute administration (2400 nmole/kg). The tolerance to this last effect developed after four days of peptide treatment. The results indicate that OXY and MIF-I can influence the processes of development of tolerance to some central depressive effects of Et-OH in rats.