| Objective: Aging SD rats induced by injection of D-Galactosewere intervened by swimming exercise (60min/d) ahead of aging, during aging andafter aging. To explore effect of aerobic exercise of different periods on brain aging,ability of spatial learning and memory and expression level of NCAM in frontal lobe.Methods:1803-month-old male SD rats were randomly divided into six groups: SD(aerobic exercise ahead of aging), ND (aging), NNa (saline control), NDs (aerobicexercise during aging), NDS (aerobic exercise after aging)and NDN (natural feedingafter aging). Each modeled large group were randomly divided into2groups: onegroup with Morris water maze test7days were designated group M, namely groupSDM, group NDM, group NNaM, group NDsM, group NDSM and group NDNM;the other group with natural feeding7days were designated group N, namely groupSDN, group NDN, group NNaN, group NDsN, group NDSN and group NDNN. Atotal of12groups, n=15. SOD activity, GSH-Px activity and MDA content in cerebralcortex were determined to evaluate the extent of brain aging. Expression level ofNCAM in frontal lobe was determined by Real-time PCR, Western blotting andimmunohistochemistry. Results：(1) State observation in rats: group ND ratscompared with group NNa revealed a lot of obvious aging signs, such as lethargy,loss of appetite, slowness, curly brown hair and Shedding.(2) Measurements of thefree radicals indexes: SOD and GSH-Px activity of group NDN rats were verysignificantly lower than group NNaN (P<0.01), MDA content was very significantlymore than that of group NNaN (P<0.01); SOD and GSH-Px activity and MDAcontent of group NDN rats had no significant difference with group NDN (P>0.05);SOD and GSH-Px activity of group NDsN rats were very significantly higher thanthose of group NDN (P<0.01), MDA content was significantly less than that of groupNDN (P<0.01); SOD activity of NDSN group rats had no significant difference withgroup NDNN (P>0.05), GSH-Px activity were very significantly higher than those ofgroup NDNN (P<0.01), MDA content was significantly less than group NDNN(P<0.01). SOD and GSH-Px activity and MDA content of6groups M and6corresponding groups N were in the same trend and had no significant difference(P>0.05).(3) Measurements of Morris water maze place navigation experiment: Spatial learning and memory of6groups M rats were initial formed on the secondday, groups SDM, NNaM, NDsM, NDSM and NDNM rats were forming a stablespatial learning and memory on the third day, group NDM rats were forming a stablespatial learning and memory on the fourth day. Escape latency of group NDSM andgroup NDNN rats on the sixth day had no significant difference (P>0.05), but theywere significantly longer than the other4groups M (P<0.01). Measurements ofSecond quadrant into the water space exploration test: the number of the times ofgroup NDM rats through the original site was significantly less than group NNaM(P<0.05), percentage of the original platform quadrant swimming distance accountedfor the total distance was significant lower than that of group NNaM (P<0.01); Therewas no significant difference between group SDM and group NDM rats in thenumber of times through the original site and percentage of the original platformquadrant swimming distance accounted for the total distance (P>0.05); the number oftimes of group NDsM through the original site was significantly more than that of thegroup NDM (P<0.05), percentage of the original platform quadrant swimmingdistance accounted for the total distance was significant higher than that of groupNDM (P<0.01); There was no significant difference between group NDSM andgroup NDNM rats in the number of the times through the original site and percentageof the original platform quadrant swimming distance accounted for the total distance(P>0.05).(4) Measurements of NCAM expression in frontal lobe: mRNA and proteinexpression level of NCAM gene in frontal lobe of group NDN rats was significantlyless than that of group NNaN (P<0.01); mRNA and protein expression level ofNCAM gene in frontal lobe of group SDN rats compared with group NDN had nosignificant difference (P>0.05); mRNA and protein expression level of NCAM genein frontal lobe of group NDsN rats was very significantly more than that of groupNDN (P<0.01); mRNA expression level of NCAM gene in frontal lobe of groupNDSN rats was significantly more than that of group NDNN (P<0.05), proteinexpression level of NCAM gene was significantly more than that of group NDNN(P<0.01). mRNA and protein expression level of NCAM gene in frontal lobe of6groups M and6corresponding groups N were in the same trend and had nosignificant difference (P>0.05). Immunoreactivities of NCAM in frontal lobe were brown, mainly located in neuronal cytoplasm beside the granular cells.(5) Thecorrelation of expression level of NCAM in frontal lobe and ability of spatial learningand memory: average escape latency and mRNA expression level of NCAM gene infrontal lobe showed a very significant negative correlation (P<0.01); the number ofthrough the original site and protein expression level of NCAM gene in frontal lobeshowed a significant positive correlation (P<0.05); percentage of the originalplatform quadrant swimming distance accounted for the total distance and mRNAexpression level of NCAM gene in frontal lobe showed a very significant positivecorrelation (P<0.01), percentage of the original platform quadrant swimming distanceaccounted for the total distance and protein expression level of NCAM gene in frontallobe showed a very significant positive correlation (P<0.01), percentage of theoriginal platform quadrant swimming distance accounted for the total distance andIOD of immunoreactivity of NCAM showed a significant positive correlation(P<0.05). Conclusion：1. Injection of D-galactose induced brain aging model ratssuccessful.2. Aerobic exercise ahead of aging did not have a favorable impact onbrain aging, ability of spatial learning and memory and expression level of NCAM infrontal lobe.3. Aerobic exercise during aging showed an effective impact on delayingbrain aging, effectively improved ability of spatial learning and memory andsignificantly increased expression level of NCAM in frontal lobe.4. Aerobic exerciseafter aging showed an effective impact on delaying brain aging, did not have afavorable impact on ability of spatial learning and memory and maintained to sustainexpression level of NCAM in frontal lobe.5. Expression level of NCAM in frontallobe is one of the mechanisms that aerobic exercise affects ability of spatial learningand memory. |
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