Study on Resistance of Brains at Different Developmental Stages Following Penty lenetetrazol-Induced Recurrent Seizures in Rats

Objective To determine if there is an early developmental resistance to seizure-induced hi ppocampal damage. Methods Five daily pentylenetetrazol-indu ced convulsions in immature rats beginning at postnatal day P10,P60 groups.In b oth groups, the latency of seizure, the latency of Ⅳ/Ⅴ grade, the lasting time of seizure and mortality of rats after seizure were used to measure sensitivity of seizure or the resistance to brain damage. Conventional histopathological me thod was utilized to observe morpbological changes and cell counting of dentate granule cells, CA 3,CA 1 and hilar neurnns. Timm histochemical technique was a dopted to study mossy fiber sprou- ting.Results 1.In the both groups(P10,P60),there were significant differences in the latency of seizure (1.07±0.55 vs 8.27±1.48 P0.05 ),the latency of Ⅳ/Ⅴ grad e (14±2.70 vs 41.6±5.22 P0.05),the lasting time of seizure(46.33±7. 65 vs 17.07±5.66 P0.05).2.In immature rats(10 days old),cell counting of CA 1, CA 3 and hilar neurons demonstrated no differences from controIs in rats,whereas adult rats with daily seizures had a significant decrease in CA 1, CA 3 neurons (8.22±l.88、5.62±1.68 vs 6.31± 1.50、3.62±1.40).In adul t rats,cell counting of dentate gradule cells demonstrated no differences from c ontrols in ratas, whereas immiture rats with daily seizures had a significant in crease(23.25±3.058 vs 16.25±1.58).3.Based on Timm staining,prominent sprou ting was seen in the CA 3 stratum pyramidal layer in all experimental rats havi ng 5 daily seizures, regardless of the age. But the degree of sprouting had sign ificant differences between the experimental groups (3.25±1.03 vs 1.5±0.92 P0.05).Conclusions 1.Though immature rats have prolonged seizures and increased susceptibility th an adult rats, resistance of hippocanipus neuron loss and mossy fiber sprouting aiterations inimmature rats is higher than adult rats. The higher resistance is based on hippocanipus morphologic alterations of immature rats followting rec urrent seizures.2.In the immature rats,recurrent seizures can also result in de ntate granule cell neurogenesis without loss of neurons,which can play an effect on mechanism of mossy fiber sprouting in immature rats. J Appl Clin Pediatr,2005,20(2):160-162