[Effects of curcumin on neurobehavior and oxidative stress in hippocampus of rats exposed to manganese]

Objective: To establish the animal model of subchronic manganism, and to explore the effect of manganese on neurofunction of rats and the protective effect of curcumin on neurotoxicity of manganism rats. Methods: From July to December 2019, 80 SPF male SD rats were divided into 8 groups according to body weight by random number table method, which were blank control group, low, middle and high dose manganese exposure group, low, middle and high dose curcumin antagonistic group and curcumin group, with 10 rats in each group. The low, middle and high dose manganese groups were given intraperitoneal injection of 5 mg/kg, 10 mg/kg and 15 mg/kg MnCl(2)·4H(2)O respectively. The low, middle and high dose curcumin antagonistic groups were given 100 mg/kg, 200 mg/kg and 400 mg/kg curcumin orally along with 15 mg/kg MnCl(2)·4H(2)O intraperitoneal injection. Curcumin group was given 400 mg/kg curcumin orally. The rats were exposed to 5 days a week, once a day for 16 weeks. After exposure, neurobehavioral tests (balance beam test, Morris water maze, passive avoidance test) were carried out in each group. Hippocampus tissues were taken for pathological examination and oxidative stress indexes were detected. Results: The balance beam test results showed that, compared with the blank control group, the scores of balance beam of the rats in the middle and high dose manganese exposure groups increased (P<0.05) . Compared with the high dose manganese exposure group, the balance beam scores of the low, middle and high dose curcumin antagonistic groups were decreased (P<0.05) .The results of Morris water maze showed that, compared with the blank control group, the escape latency of middle and high dose manganese exposure groups was prolonged from the third day (P<0.05) , and the average number of crossing the platform area of each manganese exposure group was decreased (P<0.05) .Compared with the high dose manganese exposure group, the escape latency of the middle and high dose curcumin antagonistic groups was shortened (P<0.05) , and the average number of crossing the original platform was increased (P<0.05) . The results of passive avoidance test show that, compared with the blank control group, the number of errors were increased in middle and high dose manganese exposure groups (P<0.05) . Compared with the high dose manganese exposure group, the number of errors in the passive avoidance test in the middle and high dose curcumin antagonistic groups were decreased (P<0.05) . Pathological examination showed that the rats treated with manganses had different degrees of degeneration and necrosis of nerve cells, and the structure of nerve cells was blurred and the number of nerve cells decreased. The above phenomena were improved after curcumin antagonism. The results of oxidative stress index showed that, compared with blank control group, the activity of superoxide dismutase (SOD) decreased and the content of malondialdehyde (MDA) increased in the hippocampus of rats exposed to middle and high dose of manganese (P<0.05) . Compared with the high dose manganese exposure group, the SOD activity increased and the MDA content decreased in the middle and high dose antagonist group (P<0.05) . Conclusion: Subchronic manganese exposure can reduce the balance function, learning and memory ability of rats, and damage the hippocampal nerve cells in oxidative stress state. Curcumin can improve the balance function and learning and memory ability of rats with manganese poisoning, improve the hippocampal nerve damage caused by manganese exposure, and has a certain protective effect on manganese induced neurotoxicity.