Potential protective effect of Oregano vulgare on toxic effects of naproxen on brain of Koi fish (Cyprinus carpio)

This study was performed to evaluate the effect of feeding with Oregano Vulgare essential oil supplementation on the brain tissue of Koi fish under long-term exposure to naproxen. For this purpose, 135 Koi fish (Mean weight: 1.5 gr; Average length: 6±1 cm) were divided into three groups with three replications. These fish were fed with two diets including a basic diet (BD) and an essential oil diet (OED) for 30 days. They were then exposed to naproxen (NP) for 14 days. Treatments included a control group (C): BD feeding, T1 group: BD feeding and NP toxicity, and T2 group: OED feeding and NP toxicity. Brain tissue sampling was performed at the end of the experiment. Tissue samples were examined after fixation in Bowen's solution and preparation of histopathological slides. The most common complications in T1 treatment were gliosis, vacuolation, necrosis, inflammation, and hyperemia. These complications were observed in T2 with a less destructive effect than in T1. These results showed the positive effect of feeding with oregano essential oil in reducing tissue damage exposed to NP toxicity in Koi fish. Due to the widespread use of NP and the persistence of this drug in the surface waters of the world, it is important to investigate the effects of this drug contaminant on non-target organisms. Therefore, it is necessary to identify and introduce practical strategies to reduce the adverse effects and economic losses of toxicities with these pollutants.