Effects of hippocampal neurogenesis in spatial learning and memory in rats / 中华神经科杂志

ABSTRACT

Objective To investigate the effects of hippocampal neurogenesis in spatial learning and memory,especially in spatial long-term memory.Methods Totally 24 wistar rats were randomly divided into two groupsnormal control group (NC group,n =12) and irradiation group (IRR group,n =12).We use low-dose irradiation at subgranular zone to inhibit adult hippocampal neurogenesis and new neurons were investigated by 5-Bromo-2-deoxyUridine/neuron specific nuclear protein double-labeling.Four weeks after irradiation,Morris water maze,including navigation test and space exploration assay,was used to detect spatial leaming and memory.Then,in the day 8 and day 15 after the navigation test,space exploration assay was repeated to detect spatial long-term memory.The expression levels of postsynaptic density protein 95 and synaptophysin were evaluated using western blot and real-time quantitative PCR.Results Hippocampal neurogenesis was inhibited by low dose irradiation(2.80 ± 0.44 vs 23.50 ± 1.12,t =20.21,P ＜ 0.01).After the inhibition,the escape latency did not change,while the time spent in target quadrant was significantly declined in the day 2((14.76 ±.2.04) s vs (20.47 ± 1.29) s),day 8((11.95 ± 1.34) s vs (19.52±1.43) s)and day 15((11.79 ±1.35) s vs (21.58 ±1.07) s) after the navigation test (t=2.45,P＜0.05; t =3.76,P＜0.01; t =5.39,P＜0.01).The postsynaptic density protein 95 and synaptophysin expressions were significantly decreased in IRR group.As to the RNA levels,there was also a significant difference between the two groups.Conclusion Hippocampal neurogenesis in the dentate gyrus plays an important role for the formation of spatial long-term memory.