Ultrastructural changes and effect on antioxidant capacity of Toxoplasma gondii infection in the rat hippocampus.

Objective To observe the impact of Toxoplasma gondii infection on the ultrastructure,superoxide dismutase(SOD) activity,and malondialdehyde(MDA) content in the hippocampus and spatial learning and memory.Methods Twenty adult male SD rats were randomly divided into 2 groups,a group infected with Toxoplasma and a control group.Each rat infected with T.gondii was intraperitoneally injected with 107/ml × 2 ml purified tachyzoites,and each rat in the control group was injected with 2 ml sterile saline.After 9 weeks,the learning and memory ability of rats was determined with the Morris water maze,SOD activity was determined with xanthine oxidase,MDA content was determined with thiobarbituric acid,and hippocampus mitochondria and changes in synaptic structure were observed with TEM.Results The average latent period in the Morris water maze was significantly longer(P0.05) for rats infected with T.gondii(26.07±10.08 seconds) compared to the control group(13.46 ± 5.43 seconds).SOD activity in the hippocampus of rats infected with T.gondii(49.74 ± 4.44 NUI/mg prot.) was lower than in the control group(58.19 ± 6.83 NUI/mg prot.)(P0.05).MDA content in the hippocampus of infected rats increased(4.48±0.65 nmol/mg prot.) compared to the control group(3.51±0.53 nmol/mg prot.)(P0.05).TEM results showed that rats infected with T.gondii had morphologically normal hippocampal cells,slight expansion of mitochondria,rough endoplasmic reticulum,and visible ribosomes,albeit in smaller numbers.The nuclear membrane was clear and there was no chromatin aggregation.The mitochondrial membrane was basically intact.There was a mild breakdown of myelin and many free ribosomes.Conclusion T.gondii infection can decrease hippocampal scavenging and increase oxidative stress.