Association Of Dynamin 1 Phosphorylation Status With Epileptic Seizures

Objective: Dynamin 1 is a endocytosis related proteins that is associated with epilepsy. Dynamin 1 can be dephosphorylated and mediate a high capacity synaptic vesicle(SV) endocytosis mode during elevated neuronal activity, to accommodate sudden increased pressure of synaptic transmission, regulate synaptic vesicle recycling. This study aimed to investigate if pretreated with inhibitor(different concentration) or agonist of dynamin 1 affect epileptic seizures in lithium-pilocarpine-induced rat model and continuous outbursts of action potentials(Aps) in4-aminopyridine(4-AP)-treated hippocampal slices. Furthermore our study determined the expression of dynamin 1 and phospho-dynamin 1 in the rat hippocampus after acute epileptic seizures, to explore the relationship between the different phosphorylation status of dynamin 1 and epileptic seizures.Methods: In this research, pilocarpine-induced rat model of seizure were pretreated with dynamin 1 inhibitor dynasore(different concentration)or agonist phosphatidylinositol 4,5-bisphosphate(PIP2) injected to the lateral ventricle, acute behavioral changes were observed. The expressionof dynamin 1 and phospho-dynamin 1 in the hippocampus of all the experimental rats were detected by western blotting. Using whole-cell patch clamp technique, we investigated the impact of dynasore(different concentration) and PIP2 on 4-AP media induced continuous outbursts of Aps.Result: In this study, we observed 100 and 160 μM(middle concentration) dynasore could effectively decrease percentage of spontaneous seizures, prolong seizure latency and reduce the Racine score(seizure severity) in pilocarpine-induced rat model of seizure. Although administration of PIP2 failed to change percentage and latency of spontaneous seizures, it could aggravate seizure severity. The increased expression of phospho-dynamin 1 in the hippocampus were observed in dynasore groups, especially middle concentration groups, but the phosphorylation expression level of dynamin 1 did not change in PIP2 group. Furthermore we found 10 and 20 μM(middle concentration)dynasore could significantly suppress 4-AP media induced continuous outbursts of Aps in hippocampal slices, however PIP2 had no effect on these Aps.Conclusion: This study demonstrated that dynasore, a dynamin 1inhibitor, with middle concentration suppressed epileptic seizures in vivo behavior study(100 、 160 μM) and continuous outbursts of Aps in vitro electrophysiological study(10 、 20μM), the agonist PIP2 showd anaggravation on seizure severity. In addition, 100 and 160 μM(middle concentration) dynasore increased the expression of phospho-dynamin 1,not dynamin 1, in the rat hippocampus after acute epileptic seizures.However the treatment with PIP2 did not alter the expression of phospho-dynamin 1. These results indicate that the phosphorylation status of dynamin 1 is closely associated with epileptic seizures, inhibition of dynamin 1 within a certain range may alter its phosphorylation and dephosphorylation protein expressions, affect synaptic vesicle endocytosis,and regulate the process of epileptic seizures.