Objectives: Ghrelin, a novel growth hormone-releasing peptide, was isolated from the rat stomach as an endogenous ligand for the growth hormone secretagogues receptor. The present study was planned to determine whether ghrelin affects pain threshold in mice.

Materials and Methods: Adult male BALB/C mice weighing 25–30g were used in this study. The hot plate test was conducted by placing the mouse on a metal surface maintained at 50±0.1ºC by using hot plate analgesia meter. The latency to jumping or licking a hind paw was recorded as nociceptive threshold. Animals were allowed to acclimate to the hot plate for a period of 1 week prior to the experiment. Different doses of ghrelin were intraperitoneally administered to the animals after control latencies. Control group received saline alone. Hot plate test were performed in all animals individually in 30 ^th, 60 ^th, 90 ^th and 120 ^th minutes after injection. Pain threshold values were determined and analyzed by Mann-Whitney U Test and Wilkoxon Sign Ranks Test.

Results: Ghrelin didn’t affect pain threshold throughout the experiment in 0.3pmol and 1pmol doses compared to control values. There were significant decreases in pain threshold when it is given in a dose of 3pmol in 30 ^th and 60 ^th minutes (p<0.05 and p<0.01, respectively).

Conclusion: The results of this study have presented that ghrelin may have a decreasing effect on pain threshold in mice. Further studies are needed to determine the mechanism by which ghrelin exerts its nociceptive effect. ©2005, Fırat University, Medical School