| Objective Epilepsy is a chronic disease in which recurrent local neurons are highly synchronized with abnormal discharges and cause transient brain dysfunction.With increasing in times and duration of seizures,some patients’ sensitivity to antiepileptic drugs gradually decreased,and eventually developed into drug-refractory epilepsy.Clinically,glucocorticoid can effectively control seizures and partly improve the prognosis,but the specific mechanism is not yet clear.The long-term high-level glucocorticoid environment causes hippocampal neuronal damage,affects the hippocampus’ s normal feedback inhibition of the HPA axis,and forms a vicious circle,which can lead to other chronic neurological diseases(NSDs),such as Alzheimer’s disease.These evidences suggest that different levels of glucocorticoids in different NSDs have different effects on the nervous system.Therefore,we established a rat model of epilepsy,observed the changes in glucocorticoid levels and the HPA axis,explored the potential mechanism of supplemental exogenous glucocorticoids in epilepsy,and provided a theoretical basis for clinical use of glucocorticoids in clinic.Methods 1.Establishment of temporal lobe epilepsy(TLE)model and group administration.We used lithium chloride combining with pilocarpine(i.p)to induce status epilepticus(SE)with spontaneous spontaneous seizure(SRS)episode model,and selected rats which reached the stage IV or V seizure according to the Racine grade.Group: normal group(CON),epilepsy group(EP),epilepsy+hydrocortisone group(Hydr),epilepsy+RU486 group(RU486).There are 6 rats in each group.2.Behavioral test-times of SRS was recorded by video monitoring,and Morris water maze experiment was used to evaluate the changes of learning cognition and spatial memory ability of rats.3.ELISA was used to detect the contents of CRH,ACTH and CORT in HPA axis.4.Western blot and immunohistochemistry were used to detect the expression and distribution of glucocorticoid receptor(GR).5.Neuropathology-Nissl staining and Golgi staining were used to observe the damage of neurons,dendrites and synapses.6.ELISA was also used to detect:(1)the contents of TNF-αand IL-1β;and(2)the contents of excitatory and inhibitory neurotransmitters:glutamate and GABA.Result1.SRS of TLE rats:the seizure frequency of group EP was 12.75±1.109 times a week,and that of group Hydr was 7.25±1.377 times(P<0.05).The seizure frequency of group RU486 was slightly reduced(9.75±1.493),but there was no statistical significance compared with group EP.2.Supplementation with exogenous CORT contributing to improve the learning and cognitive function of TLE rats:the results of water maze showed that comparing with normal rats,the latency and swimming distance of epileptic rats increased,the search path was"marginal",and the crossing times of the platform decreased.After hydrocortisone supplementation,the swimming distance and latency of epileptic rats decreased significantly(P<0.05),and the crossing times increased(P<0.05);the swimming distance and latency of RU486-rats decreased(P<0.05),but there was no difference in the crossing times(P>0.05).3.Supplementation with exogenous CORT contributing to better the dysfunction of HPA axis and signal pathway:comparing with normal rats,the serum CORT level of epileptic rats decreased,and the levels of ACTH and CRH increased in varying degrees.After hydrocortisone supplementation,the level of CORT increased,ACTH decreased,and CRH decreased.In group RU486,the level of CORT increased,but ACTH and CRH decreased without statistical difference.Western blot and immunohistochemistry showed that the expression of GR protein in brain tissue of epileptic rats decreased,while that in group Hydr and RU486 increased in varying degrees;immunohistochemistry showed that the number of GR positive cells in hippocampal CA1 area of epileptic rats decreased after hydrocortisone treatment,the number of GR positive cells increased significantly,but group RU486 did not.4.Supplementation with exogenous CORT contributing to reduce the damage of hippocampus:Nissl staining results showed that the neurons in CA1 and CA3 areas of hippocampus in epileptic rats were obviously lost,and the structure was destroyed.Hydrocortisone treatment can significantly improve these damages,and group RU486also improved to some extent.Golgi staining showed that bryophyte fiber germination increased in the dentate area of epileptic rats,while hydrocortisone and RU486inhibited the abnormal fiber germination in varying degrees.5.Supplementation with exogenous CORT can inhibit the inflammatory reaction in SE rats:comparing with group CON,TNF-αand IL-1βincreased significantly(P<0.05),and these two indexes decreased significantly after hydrocortisone treatment(P<0.05);RU486 decreased to some extent,but there was no statistical difference.6.Supplementation with exogenous CORT adjusts the imbalance of neurotransmitters:the level of glutamate in group EP was significantly higher than that in group CON,and the level of GABA was significantly decreased;after hydrocortisone and RU486 were used,the balance of the two neurotransmitters was restored in varying degrees.Conclusion1.Epilepsy can cause HPA axis dysfunction in rats,maintain glucocorticoid helping to restore the balance of excitability and inhibitory neurotransmitters,and reduce sprouting of mossy fibers in the dentate gyrus,thus reduce seizures;2.Glucocorticoid can reduce the inflammatory response in the brain of epileptic rats and neuronal damage in the hippocampal CA1 and CA3 areas,which may be related to the improvement of cognitive function;3.RU486 fails to significantly inhibit seizures,but it can slightly improve brain function;4.Exogenous glucocorticoid and RU486 can’t change the composition ratio of GRβ/GRα significantly. |
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