Abilities of learning and memory could be improved by behavioral training in SD rats received low doses X-ray

Abstract

Objective To explore the effect of behavior training on abilities of learning and memory in young SD rats received low doses of X-ray and their relevant mechanism. Methods A total of 48 SD rats aged 35 d were randomly divided into irradiated group, training group and control group (n=16); rats in the irradiated group and training group received X-ray once daily for seven d; rats in the training group also received behavior training. Abilities of learning and memory were detected by Morris water maze test; changes of N-acetyl aspartate/creatine (NAA/Cr) in the hippocampus were observed; the protein expression levels of cytochrome c oxidase IV (COXIV) in hippocampal regions were observed by immunofluorescence staining and Western blotting. Morphology of neurons in hippocampal CA1 region was detected by HE staining, and mitochondrial morphology was observed via transmission electron microscopy. Results (1) As compared with that in control group (1.873 ± 0.032), the ratio of NAA/Cr in the irradiated group (1.611±0.013) was significantly decreased, while that in the training group (1.870±0.018) was significantly higher than that in the irradiated group (P 0.05). (3) Immunofluorescence indicated decreased COXIV protein expression in the CA1 area of irradiated group and increased COXIV protein expression in the CA1 area of training group; Western blotting showed that the COXIV protein expression in the hippocampal regions of irradiated group (0.298 ± 0.049) was significantly decreased as compared with that in the control group (0.998 ± 0.056, P 0.05). (4) Karyopyknosis and more damaged mitochondria were found in the irradiated group, while more normal neurons were observed in hippocampal CA1 area of the control and training groups by HE staining. Conclusion Learning and memory abilities of SD rats received low doses of X-ray could be recovered by behavior training, which could be related to the increment of COXIV protein expression and mitochondria improvement by behavior training, and neuron damage in the hippocampus would be reversible in an extent. Key words: Radiation, ionizing; Learning and memory; Mitochondria; Magnetic resonance spectroscopy