Abstract: Abstract: Objective To observe the influence of molar-missing on apoptosis of hippocampus CA1 neurons and expression of casepase-3 in hippocampus neurons of young rats ,and to investigate the possible mechanism of juvenile molar-missing on hippocampus neural cell apoptosis in young rats. Methods 60 male SD rats(at the age of 4~5 weeks) were randomly divided into control group and experimental group, 30 in each group .And then 30 rats were randomly divided into three groups(4-week group, 8-week group and 20-week group) based on when the modeling ends down to observe the expression of casepase-3 protein by using HE staining and immunohistochemistry, and to observe the dynamic changes of nerve cell apoptosis in rat hippocampus by using TUNEL method. Results: 1. The morphology and structure of hippocampus CA1 cells were normal in the control group, and there were no significant pathological changes. The cells in the experimental group were swollen, vacuoles appeared, the structural arrangement became disordered, and the neuron cells were significantly reduced.2. With time variation(4,8,20 weeks), positive cells in hippocampus CA1 region of experimental group by the number increased, and the difference was statistically significant (P = 0.000), while in the control group there was no statistical difference (P = 0.301) in casepase-3 expression. The differences were statistically significant in casepase-3 expression between any two groups (P < 0.001). 3.The TUNEL positive cells in experimental group had a statistically significant difference (P = 0.000). The TUNEL positive cells in control group had no significant difference (P = 0.276) . There was a statistically significant difference in the number of TUNEL positive cells between any two groups (P < 0.001).Conclusion: Longrun chewing stimulation decrease may increase apoptosis in hippocampus of rats and may increase the expression of casepase-3 protein at the same time. The results suggest that the long-term molar deletion in rat hippocampus induces the development of apoptosis of hippocampus tissue cells.

Key words: Key words : molar-missing, Learning and memory, Hippocampus tissue, Cell apoptosis