The Role Of Fyn Pathway Mediated By5-HT₆R In Synaptic Plasticity Modification Of Epileptic Rats

ObjectsIn this study we aimed to observe the variation of5-HT6R and synapticplasticity indictors in different period after epileptic seizures;test the effect ofSB271046on cognitive disorder of epileptic rat and explore the potential mechanismin synaptic plasticity.Methods1. Experimental animals and groups:（1）54male adult Sprague-Dawly rats weredivided into2groups,vehicle control group(n=9) and pilocarpine(PILO) treatedgroup(n=45). The success SE of PILO group then was divided into5subgroupsaccording to the different time after seizures(1day、7day、15day、30day and60day).（2）40male adult Sprague-Dawly rats were divided into4groups,vehicle controlgroup(n=10), epilepsy group(n=10),epileptic rats administrated Hp-β-CD（EP+Hp-β-CD）(n=10) and epileptic rats treated with SB271046（EP+SB271046）(n=10).2. Establish epileptic model: intraperitoneal injection PILO(30mg/kg) after16-18h LiCl(127mg/kg) was administered, observed behavior changes continuously30min to decide the success of status epilepticus（SE）, according to Racine classify(seizures up to IV and continue more then30min was supposed SE).3.Observe the mossy fiber sprouting of epilepsy subgroups by Timm’scolouration.The level of5-HT6R, synaptophysin and GFAF were detected byReal-time PCR.4. Fyn signaling pathway related proteins,including Fyn、ERK1/2、p-ERK1/2weredetected by western blot and the m RNA level of Fyn were tested by Real-time PCR.synaptic ultrastructure in hippocampal CA1region was observed by electronmicroscopy；observe the mossy fiber sprouting by Timm’s colouration; astrocyteactivation was evaluated with immuno-histochemistry staining;the level of GFAP,GluR and NMDAR1were tested by Real-time PCR.Results1. The degree of mossy fiber sprouting and level of synaptophysin increasedgradually as time progresses. p(60d vs30d)>0.5.The level of GFAP and5-HT6R both increased in30days(p<0.001) and60days（p<0.001)3. the antagonist of5-HT6R SB271046increase Fyn and pERK1/2/ERK1/2proteinexpression,after administating SB-271046，the mRNA level of Fyn、pERK1/2/ERK1/2increased76%（p<0.01）、130%（p<0.05）.4. SB271046can ameliorate synapticultrastructure in hippocampal CA1region;inhibited astrocyte activation andhyperplasia in dentate gyrus of hippocampus in epileptic rat; alleviated mossy fibersprouting in hippocampal CA3region of epilepsy.increase indication related tosynaptic plasticity, including GluR（p<0.0001)、NMDAR1（p<0.0001).ConclusionsLicl-PILO induced epileptic seizures rat is a good model for imitating humantemple lobe epilepsy. The epileptic rats display mossy fiber sprouting,astrocyteactivation and synapse dysfunction，and5-HT6R activity may plays an important rolein these synaptic plasticity variations.SB271046may activate5-HT6R-Fyn/ERK1/2signaling pathway，through mediating synaptic plasticity changes ameliorate cognitiveimpairment and SRSs of epileptic rats.