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.

Objective To explore the effect of aerobic exercises on synaptic plasticity and expression of PDE-4 in hippocampus during the aging process of rats.Methods Forty-five adult male SpragueDawley rats were randomly divided into a control group(group C),an D-galactose induced aging group (group A) and an D-galactose induced aging & aerobic exercise intervention group(group AE).All rats were induced aging for 6 weeks and group AE was given swimming exercise intervention of a moderate load simultaneously.Then Nissl's staining was conducted to observe the neurons in the dentate gyrus(DG).The immunofluorescence was employed to detect the number and density of synaptophysin (Syp) and metabotropi glutamate receptor 1(mGluR1).And the expression level of Phos-phodiesterase 4(PDE-4) mRNA and protein was observed using the,real-time PCR and Western blotting.Results Compared with group C,senile signs such as mental retardation,lethargy and tardy movement,significantly less neurons in the hippocampus,bigger cell spacing and shallower Nissl body in the cytoplasm were observed in group A.The integrated optical density(IOD) values of Syp and mGluR1 in group A decreased significantly compared to group C(P＜0.01),while those of group AE were significantly higher than group A(P＜0.01).The expression of PDE-4 mRNA and protein in Group A increased significantly compared with group C (P＜0.01),but that of group AE was significantly lower than group A (P＜ 0.01).The expression of PDE-4 mRNA was negatively correlated to the IOD value of Syp and mGluR1 (P＜0.01,P＜0.05).Conclusions The aerobic exercises can improve the morphology of hippocampal neurons and keep the number and density of Syp and mGluR1 at a certain level to maintain the synaptic plasticity,so as to improve brain function and delay the aging process.Moreover,exercise may affect brain function through down-regulating the expression of the PDE-4 gene.