Age-Dependent Feature of Damage of Hippocampus at Different Maturational Stages after Repeated Seizures in Rats

Objective To observe age-dependent feature of damage of hippocampus to different maturational stages rats after kindling repeated seizures.Methods The effects of 5 daily pentylenetetrazol-induced convulsions in different rats beginning at postnatal day 10,20,60(P10,P20,P60)were evaluated.In the 3 groups,Thionin staining method was utilized to observe morphological changes and cell counting of dentate granule cells,CA3,CA1,and hilar neurons.Timm's method of silver sulfide staining was adopted to observe the mossy fiber sprouting.Results 1.Cell counting of CA1,CA3 and hilar neurons in P10 and P20 groups demonstrated no differences from controls in rats,whereas P60 with daily seizures had a significant decrease in CA1,CA3 neurons(8.22±1.88,5.62±1.68 vs 6.31±1.50,3.62±1.40)(t=2.246,2.587 Pa0.05).In P60 group,cell counting of dentate granule cells demonstrated no differences from controls in rats,whereas P10 with daily seizures had a significant increase(23.25±3.058 vs 16.25±1.58)(t=5.752 P0.01).2.Based on Timm staining,prominent sprouting was seen in the CA3 stratum pyramidal layer in all experimental rats having 5 daily seizures,regardless of the age.But the degree of sprouting had significant differences among the experimental groups(F=6.514 P0.01).Conclusions 1.The resistance of hippocampus neuron loss and mossy fiber sprouting alterations in immature rats are higher than that of adult rats.The higher resistance is based on hippocampus morphologic alterations of immature rats following recurrent seizures.2.Neurons of dentate granule increases significantly after repeated seizures,which can be the initiative mechanism for mossy fiber sprouting in immature rats.