Abstract: Objective: The purpose is to investigate the effect of long-term heavy load swimming exercise on the spatial learning and memorizing abilities and the expression of neural cell adhesion molecule(NCAM) in hippocampus of SD rats. Methods: 40 male rats were randomly divided into 4 groups as follows(n=10 in each group): control group(C), control group and Morris maze(CM), and both were conventionally bred without intervening; 7 weeks of moderate swimming exercise were given to heavy load exercise group(HL) and Morris maze group (HLM). After 7 weeks, the brain of the C and HL group’s rats were taken out to test the mRNA and protein of NCAM through real-time PCR and Western Blotting. The navigation and space exploration ability of CM and HLM were tested through Morris water maze. Results:1.In the period of swimming, the weight of HL group rats was significantly lower than that of C group at 5, 6 and 7 weekends(p<0.01); the weight of HLM group rats was significantly lower than that of CM group at 4, 5, 6 and 7 weekends (P < 0.05,P < 0.01).2.After Morris maze training, the early 3 days evasion incubation period of the two groups and the last 5 days ability of learning and memory had a significantly difference(p<0.01). The average escape latency of CM group from 2 to 10 days was significantly lower than the first day (p<0.01), and it became significantly lower from 3rd to 10th days than the second day(p<0.05,p<0.01); the average escape latency of HLM group from the 2nd to 10th days was significantly lower than the first day(p<0.01),and it was significantly lower from 4th to 10th days than the second day(p<0.05,p<0.01). After Morris maze training, the average traversing times of HLM group were more than those in CM group (p>0.05). 3. The expression of NCAM gene and protein of the HL group rats were significantly more active than the C group rats(P<0.05).Conclusion: Although 7-weeks of long-term heavy load exercise can shorten the evasion incubation period of locating swimming and enhance the passing frequency of spatial exploring of rats, within the increase of load and the accumulation of fatigue, the rats behaved more unstably and it will affect the formation of learning and memory in rats; long-term heavy load exercise is conducive to the promotion of NCAM expression in rats hippocampus, which shows that the mechanism may be associated with the repairmen of injured nerves.

Key words: exercise, learning, memorizing, hippocampus, NCAM