Study Of SSmRNA,PVmRNA Expression In GABAergic Interneurons In The Hippocampus Of Pilocarpine-treated Rats

Background and objective:Temporal lobe epilepsy(TLE) is one of the most common refractory epilepsy in clinical,but so far the epileptogenesis is still not clear.The enhancement of excitatory circuit and decrease of inhibitory circuit in the hippocampus play an important role in temporal lobe epilepsy.Researches revealed although the foundation of excitatory circuit participated in the generation of temporal lobe epilepsy,it still couldn't fully explain the reasons of spontaneous seizures.So currently GABAergic interneurons which are deeply associated with hippocampal inhibitory circuit have gradually been the research hotspot.Loss of GABAergic inhibitory interneurons is the main reason of decrease of GABAergic inhibit.However,reports about the change of GABAergic interneurons are different,and they mainly derived from epilepsy induced by kainic acid or electrock.Our colleague finded SS positive GABAergic interneuron and PV positive GABAergic interneuron experienced remarkable change during the course of epilepsy induced by pilocarpine.But the change about gene expression is still uncertain and what is the relation between positive interneurons and gene expression is still a question.So,further research is needed about gene expression in GABAergic interneurons in temporal lobe epilepsy.In this research,we observed the change of SSmRNA and PVmRNA in GABAergic interneurons in the hippocampus of rats induced by pilocarpine,in order to reveal the roles of SSmRNA and PVmRNA of GABAergic interneurons in the generation and compensation of temporal lobe epilepsy,and hope to provide more theoretical evidence for research in future.Methods:1) 96 healthy male SD rats were divided randomly into epilepsy groups(n=64) and control groups(n=32).Two groups were divided randomly into 8 subsets at 2,6hr and 1,3,7,15,30,60d after pilocarpine or normal sodium(NS) intraperitoneal injection.The models of epilepsy were established by intraperitoneal injection of pilocarpine and lithium,while the controls were injected with NS.The degree of seizure was judged according to Racine standard.2) Nissl stain was used to observe the pathological changes of hippocampus.3) In situ hybridization method was used to detect expression of SSmRNA and PVmRNA in different domains of the hippocampus at different time points. Results:1) After lithium-chloride and pilocarpine administration,87.5%rats were induced SE successfully,and the moratily rate was 17.19%.2) Nissl stain revealed,in the experimental group,loss of hippocampal neurons was most evident on 3～7d and 60d after SE. Significant loss of neurons and pyramidal neurons was present in hilus and area CA(p＜0.01),while the loss of granular cells in the dentate gyrus was relatively slight(p＜0.05).3) In the experimental group,the number of SSmRNA in GABAergic interneurons decreased in each hippocampal domain,and was least on 3d after SE(p＜0.01).In latent period,the number of SSmRNA in interneurons recovered partially.In chronic period,the number of SSmRNA in interneurons in area CA3 even exceeded the control group(p＜0.05),while in hilus(p＜0.01)and CA1 area(p＜0.05)was still less than normal levels.4) In the experimental group,the number of PVmRNA in interneurons decreased in hilus of the hippocampus untill 60d after SE(P＜0.01).The number of PVmRNA in interneurons in CA1 area decreased and was least on 3d after SE(P＜0.01),and then recovered partially,while was still less than normal levels(p＜0.05).There were no evident change of PVmRNA in interneurons in early phase in CA3 area(p＞0.05),the number of it increased in chronic period(p＜0.01). Conclusions:1) Loss of SSmRNA,PVmRNA expression in GABAergic interneurons may play an important role in the generation of temporal lobe epilepsy.2) Recover of SSmRNA,PVmRNA expression in GABAergic interneurons in chronic period may be relative to compensation of temporal lobe epilepsy.3) The number of GABAergic interneurons experience changes partially due to changes in mRNA expression,but changes in mRNA expression in the neurons is not the only reason of neuron number changes.