Abstract:The effects of nociceptin(1-13)NH 2 (N/OFQ(1-13)NH 2 ) and its structural analogue [Orn 9 ]N/OFQ(1-13)NH 2 on acute carrageenan (CG)-induced peripheral inflammation and paw antioxidant status were studied. CG was injected intraplantarly in the right hind paw of rats and the volume of the inflamed paw was measured each 30 min for a period of 4h. When administered simultaneously with CG, N/OFQ(1-13)NH 2 decreased the paw volume, whereas if injected 15 min before CG it had no effect. [Orn 9 ]N/OFQ(1-13)NH 2 produced the opposite effects at the same time-intervals of its administration. We also investigated whether these neuropeptides influence CG-induced changes in cell antioxidant system, especially at the 4 th hour of CG administration. CG alone decreased the glutathione level and superoxide dismutase activity, as measured in post-nuclear homogenate of the inflamed paw. However, CG injection increased glutathione peroxidase and glucose-6-phospate dehydrogenase activities, while the activity of glutathione reductase was unchanged. The peptides themselves did not change all measured parameters. Moreover, neither N/OFQ(1-13)NH 2 nor [Orn 9 ]N/OFQ(1-13)NH 2 modified CG-induced changes in the antioxidant status, regardless of the time of their injection (simultaneously or 15 min before CG). The present results suggest that N/OFQ(1-13)NH 2 and [Orn 9 ]N/OFQ(1-13)NH 2 most likely affect the neuronal inflammation, rather than act as pro-or antioxidants.