Résumé
Objective To observe the effect of aerobic exercises on the expression of synaptophysin (SYP)and postsynaptic density protein-95 (PSD-95) in the prefrontal lobe of brain-aging rats induced by D-galactose (D-gal) and to explore the underlying mechanism of aerobic exercises relieving learning and memory deficits in the brain-aging process.Methods Thirty-six 3-month-old male Sprage-Dawley rats were randomly divided into a saline control group (C),a D-gal control group (D),and a D-gal and aerobic exercises group (DE),each of 12.The rats in both group D and DE were injected D-gal (100 mg/kg body weight) abdominally every day for 6 consecutive weeks,while those in group C were injected the same amount of saline.Meanwhile,the rats in group DE had performed aerobic swimming for 1 hour daily,while the other two groups did not do any exercises.Then,the Morris Water Maze (MWM) test was performed to estimate the learning and memory abilities.The immunofluorescence technology,Western blotting and real-time PCR were used to determine the expression levels of SYP,PSD-95,SYP mRNA and PSD-95 mRNA in the prefrontal lobe.Results In the process of navigation training,all animals' escape latencies shortened gradually,indicating that each rat was able to learn to locate the submerged platform.The rats in group C and DE showed best performance on day 3 and no significant improvement was observed thereafter,whereas those in group D improved at a slower pace,and reached maximal performance on day 5.On the 2nd,3rd and 4th days of the navigation training,the average escape latency of group D was significantly longer than that of group C and group DE (P＜0.05),while on the 1st,5th and 6th days,there was no significant difference among the 3 groups.In the probe trial,rats in group D spent significantly less time in the target quadrant compared with both group C and DE (P＜0.05),and rats in group C and DE crossed where the platform was fixed significanlty more often than group D (P＜0.05).The expression levels of SYP and SYP mRNA in the prefrontal lobe of rats in group D were significantly lower than group C (P＜0.01),and group DE (P＜ 0.05).Compared with group C,the expression levels of PSD-95 and PSD mRNA in the prefrontal lobe of rats in group D declined significantly (P＜0.01).There was no significant difference in PSD-95 expression between group D and DE,but the level of PSD-95 protein molecule of group DE was significantly higher than that of group D (P＜0.05).Conclusions The aerobic exercises can ameliorate the deficits of SYP and PSD-95 expression in the frontal cortex of aging rats induced by D-gal to some extent,and improve their learning and memory abilities.