The Effects Of Jab1Pathway Mediated By5-HT₆Receptor On Learning-memory In Epileptic Rats

ObjectsTo explore the potential mechanisms that are involved in reduction of epilepticseizures and antiamnesic effects.we investigate the effects of5-HT₆receptorantagonist SB-271046on Jab1pathway on learning-memory in lithium-pilocarpine-induced epileptic rats,Methods1. Experimental animals and groups:50male adult Sprague-Dawly rats were dividedinto2groups,vehicle control group（n=10） and pilocarpine（PILO） treated group（n=50）.The success SE of PILO group then was divided into4groups：control group（HP-CD,injected to lateral ventricle （LV）with HP-β-CD,4ul）,10ug-SB271046group（10ug-SB, injected to LV with SB-271046,4ul）,20ug-SB271046group（20ug-SB,injected to LV with SB-271046,4ul）,30ug-SB271046group（30ug-SB, injected toLV with SB-271046,4ul）;While without SE or died were knockout of theexperiments.2. Establish epileptic model: intraperitoneal injection PILO（30mg/kg） after16-18hLiCl（127mg/kg） was administered, observed behavior changes continuously30minto decide the success of status epilepticus（SE）, according to Racine classify （seizuresup to IV and continue more then30min was supposed SE）.3.Rats’ spontaneous recurrent seizures（SSRs） were observed according to Veliskovaand Goffin’s criteria.4. With the help of brain solid positioner and watson《rat brain stereotaxic atlas》,therecording electrode was inserted in right frontal lobe cortex and SB-271046orHP-β-CD was microinjected into right LV in0.5,1,2,4,8,16hours.5. The changes of Jab1pathway,including Jab1,c-Jun and p-c-Jun, in prefrontal cortex,hippocampus and striatum were observed and analysed by Western blot. 6.The apoptotic cells in prefrontal cortex, hippocampus and striatum were observedand anlyized by Tunel/HRP2weeks after microinjection into LV.Results1.Behavioral results:（1） Successful rate and survival rate of pilocarpine-inducedepileptic model: In the first experiment, the successful rate and the survival rate were72.55%and42.84%. In the second experiment, the successful rate and the survivalrate were85%and52.94%. In the third experiment, the successful rate and thesurvival rate were83.4%and56.62%.（2） SSRs in chronic period: HP-CD group and all of drug-dose groups were observedSSRs,and between3-4attack stage.After the injection of SB-271046,the frequence ofSSRs was decreased;To compare with10ug-SB group,the frequence of SSRs of20ug-SB group and30ug-SB group were obviously reduced.However SB-271046showed no effect on reduction the degree of seizures,according to Veliskova criteria.seizures.2. Tunel/HRP:①To campare with Vehicle group,the numbers of the apoptotic cells indifferent brain zones（Cortex、Hippocampus、Striatum）were increased,especially inHippocampus.②After injection to LV with SB-271046,the numbers of the apoptoticcells in different brain zones were decreased,the most obvious zone washippocampus.,then striatum.③After injection to LV with SB-271046,the numbers ofthe apoptotic cells in different dose groups were reduced,especially30ug-SB group.3. Western blot:①The drug of SB-271046had time-dependent and dose-dependentmanners, in line with the pharmacokinetic characteristics.What’s more,its biologicaleffects maintained for at least16hours.②To compare with Vehicle group,theexpression of Jab1protein had no changes,but the phosphorylation level of c-Junprotein was increased, hippocampus was the most apparent place.③After injectionto LV with SB-271046, the expression of Jab1protein and the phosphorylation levelof c-Jun protein were decreased in different dose, especially30ug-SB group.④TheJab1in Hippocampus where SB-271046suppressed was the most obvious,while thephosphorylation level of c-Jun protein in Cortex was the most apparently reduced. Conclusions1、In chronic epileptic rats,the numbers of the apoptotic cells were increased,and c-Junwas overexpressed.2、5-HT₆receptor antagonist had time-dependent and dose-dependent manners,andhad a characteristic of tissue selectivity.3、SB-271046maybe play the biological effect by suppressing the Jab1pathway,thento reduce the seizures and improve the cognitive impairment in epileptic rats.4、5-HT₆receptor antagonist could suppress the apoptosis,futhermore reducing theoverexpression of c-Jun.