The Signal Mechanisms Of Hippocampus Neuron Apoptosis Of The Newborn Rat After Maternal Separation In Neonatal Period

Objective To detect the apoptosis change and the expression level ofCaspase-3, Caveolin-l in developing rats’hippocampal neuron after matermalseparation, and explore the potential mechanism of rats’ abnormal behaviorresulted from maternal separation in neonatal period.Methods48Wistar neonatal rats were divided equally and randomly intoNgroup(n=24) and control (C) group(n=24).Each group were separated into3subgroups(n=8). Rats in N group were separated from the dams for3h/d(8:00-11:00am) from postnatal day2to postnatal day21, rats in C groupwere not disturbed and remained in the home cage with the dam.Rats in the twogroups were killed to get brains and prepare for sections on day7,14and21respectively after postnatal.Terminal transfer nick end labeling(TUNEL) wereused to detect the apoptosis of hippocampal neuron cells, the expression ofCaspase-3and Caveolin-l in hippocampal neuron cells were evaluated bystreptavidin-peroxidase immunohistochemisty.Image-Pro Plus software wereused to semiquantitative assessment the immuneohistochemical images.Results (1) The appearances of claybank particles were used as a positivejudgment standard. TUNEL-positive cell and Caspase-3were mainly expressedin the hippocampal pyramidal cells; Caveolin-l was mainly expressed in theglias of hippocampus.(2) The apoptosis changes in hippocampal neuron cells:The number of TUNEL-positive neuron cells were the most in each group at7d,with age increasing, the number gradually decreased in the N group and C group.Compared with C groups at the same time,N groups (apoptotic index:7d:22.62±0.68vs18.38±2.26;14d:12.23±0.97vs9.51±1.44;21d:8.14±0.93vs5.60±0.63) were significantly increased(P<0.01).(3)The expression of Caspase-3inhippocampal formation: The expression level of Caspase-3in the N groupwas the highest at7d of each group, with age increasing, the expression levelgradually decreased in the N group and C group.Compared with C groups at thesame time,N groups (7d:0.29±0.03vs0.24±0.01;14d:0.22±0.01vs0.18±0.02;21d:0.16±0.01vs0.13±0.01)were significantly increased (P<0.01); The resultsof Caspase-3were coincident with those of TUNEL.(4) The expression ofCaveolin-l in hippocampal formation: the expression of Caveolin-1in eachgroup were gradually increased with age increasing, compared with C groups atthe same time, N groups (7d:0.13±0.01vs0.12±0.01) were not significantlydecreased (P＞0.05),(14d:0.19±0.01vs0.22±0.01;21d;0.24±0.01vs0.29±0.01)were significantly decreased(P<0.01).Conclusion Maternal separation in neonatal period increase thehippocampal neuron apoptosis and the expression of Caspase-3and decreasethe expression of Caveolin-l. Which are possibly related to the mature rats’abnormal behavior in the condiction of consecutive maternal separation in earlylife.