A gastroprotective effect occurs when alpha(2) receptors are innervated. The dextro isomer of medetomidine, dexmedetomidine, is a highly selective alpha(2)-adrenoreceptor agonist. The aim of this study was to investigate whether dexmedetomidine has an antiulcerative effect and to show whether the antiulcer mechanism of dexmedetomidine is linked with oxidant/antioxidant parameters. The antiulcerative effect of dexmedetomidine was studied in an indomethacin-induced ulcer model, and some oxidant/antioxidant parameters were measured in these gastric tissues. Whereas the average ulcerous areas for the groups that received 10, 25, 50, and 100 mu g/kg dexmedetomidine doses were 29 +/- 4.2, 8 +/- 2.1, 0 +/- 0 and 0 +/- 0 mm(2), respectively, the ulcerous area was 52.1 +/- 4.5 mm(2) in the indomethacin control group and 0.5 +/- 0.2 mm(2) in the famotidine group. In conclusion, the alpha(2)-adrenoreceptor agonist dexmedetomidine showed a significant antiulcerative effect in rat gastric fissile at all doses. This antiulcerative effect is stronger with increasing dosage; at the 50 and 100 mu g/kg doses, no ulcerous areas were observed. In light of these results, we conclude that there is a correlation between antiulcer mechanisms and alpha(2)-receptor activation. In rats given dexmedetomidine, all of the investigated antioxidant parameters increased, except for catalase (CAT). Conversely, aside from myeloperoxidase (MPO), all oxidant parameters decreased. Therefore, oxidant/antioxidant parameters play a role in the antiulcer mechanism of dexmedetomidine.