MIF-1 antagonizes warm-, but not cold-water stress-induced analgesia: dissociation from immobility

Forced swimming in warm or cold water can lead to immobility and analgesia in mice. In this report we demonstrate that the peptide MIF-1 (Pro-Leu-Gly-NH2) was able to attenuate the analgesia induced by swimming in warm water, but not that induced by swimming in cold water. In addition, we show that the analgesia and the immobility may be differentially mediated since MIF-1 was able to reduce the immobility at doses different from those necessary to reduce the analgesia. These results confirm previous research indicating that MIF-1 may act as an anti-opiate and further demonstrate that MIF-1 affects analgesia induced by stress.