Plasticity Of Neuronal Dendritic Spines In Epilepsy Rats Induced By Kainic Acid

Objective:To study the plasticity characteristics of dendritic spines of CA1 pyramidal cells and dentate gyrus granule cell in duration of sensitive formation of epilepsy on hippocampal.Methods: SD rats were used to produce epilepsy model by subcutaneous injection of kainic acid (10mg/2ml/kg) at neck. Animals, which attack severely in Level 4, meet the requirements of epilepsy models. Respectively after the onset of 3d and 7d, the rats were anesthetizes and the brains were fixed by 4% Paraformaldehyde perfusion through the heart. The brains were removed and made of blocks of brain tissue including hippocampal structure. The brain tissue blocks were performed with Golgi staining. After that, the blocks were embedded with collodion, and then sliced. Nikon light microscope with the imaging system and NIS-Elements Br image analysis software was used to observe and analyeze dendritic spine morphology in the hippocampal dentate gyrus molecular layer and the lacunar layer of CA1. In the normal control group,the kainic acid is replaced with normal saline.Results:1 The inner bend of molecular layer changes in dendritic spinesDendritic spine density in the acute attack of epilepsy was significantly increased after 3 days, and 7 days after the onset of dendritic spine density continues to increase, significantly more than the normal control and KA3d group (P <0.05). The short spines without neck of KA3d and KA7d groups was significantly higher than the number of the control group(P <0.05), but no significant difference between the two. Compared with control group, KA3d group did not change significantly the number of long spine with neck, but the average length of long spine with neck decreased (P<0.05); Compared with control group and KA3d group, the number of long spine with neck in KA7d group significantly increased (P <0.05 ). And the average length of the long spine in KA7d group return to the level of control group. The ratio of long spine and the total number of dendritic spines in KA3d group showed declining trend, while KA7d group was significantly increased (P <0.05).1 The outer bend of molecular layer changes in dendritic spinesDendritic spine density in the acute attack of epilepsy was significantly increased after 3 days, and 7 days after the onset of dendritic spine density continues to increase, significantly more than the normal control and KA3d group (P <0.05). The short spines without neck of KA3d and KA7d groups was significantly higher than the number of the control group(P <0.05), but no significant difference between the two. Compared with control group, KA3d group did not change significantly in the number and average length of long spine with neck; Compared with control group and KA3d group (P <0.05 ). And the average length of the long spine in KA7d group return to the level of control group. The ratio of long spine and the total number of dendritic spines in KA3d group showed declining trend, while KA7d group was significantly increased (P <0.05).3 To compare the changes of dendritic spines between inner and outer bends of dentate gyrus molecular layerIn KA3d group the dendritic spine density of the inner bend was significantly lower than the outer (P <0.05). KA7d group, take-no significant difference between the density of dendritic spines of the inner and outer bends, but the outer spines are the number of long spine with neck and its proportion in the total number of dendrites were significantly more than the inner zone (P <0.05).4The dendritic spines in lacunar layer of hippocampal CA1 area.3 days after acute attack of epilepsy, the number of dendritic spines showed a downward trend, and 7 days after the onset, it was significantly reduced in number of dendritic spines (P <0.05).In short, the density of dendritic spines in the inner and outer bands of dentate gyrus molecular layer have continued to increase within a week in epilepsy, 3 days in the seizures mainly in short dendrites, from the onset after 3 days to 7 days after the onset of the mature Neck-of-spine have increased significantly. Through, by the comparison between outer and inner bends, 3 days after onset of epilepsy, the number of dendritic spines in the outer band take away significantly more than that in the inner band, in 7 days after seizures, there was no significant difference in the density of dendritic spines between the inner and outer bands, but the number of long spine with neck in outer spines was significantly more than that of inner belt.3 days after the seizure, the long spines with neck in the inner band was significantly shorter and atrophy.Lacunar layer of CA1 dendritic spines density in 3 days after seizures,show no significant drop,and decreased significantly after 7 days.Conclusions:1 In the formation of seizure susceptibility , obvious morphological changes occur in the dendritic spines of dentate gyrus molecular layer and CA1 dendritic spines lacunar layer, which may be involved in formation mechanism of seizure susceptibility.2 The plasticity of dendritic spines in outer molecular layer of dentate gyrus is more significant than that in the inner .3 The dentate granule cell plasticity in dendritic spines may lead to the re-injury of CA1 pyramidal cells.