The Effects Of SB-271046on Learning-memory In Lithium-pilocarpine-induced Epileptic Rats

ObjectsTo investigate the effects of5-HT6receptor antagonist SB-271046on learning-memory in lithium-pilocarpine-induced epileptic rats,we sought to determine potential mechanisms that are involved in reduction of epileptic seizures and antiamnesic effects.Methods1. Experimental animals and groups:50male adult Sprague-Dawly rats were divided into2groups,vehicle control group(n=10) and pilocarpine(PILO) treated group(n=50). The success SE of PILO group then divided into3groups:mode control group (HP-CD, injected to lateral ventricle (LV) with HP-β-CD,4ul),10ug-SB271046group (1Oug-SB, injected to LV with SB-271046,4ul),20ug-SB271046group (20ug-SB, injected to LV with SB-271046,4ul);While without SE or died were knockout the experiments.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, seizure up to IV and continue more then30min was supposed SE.3. With the help of brain solid positioner and watson 《rat brain stereotaxic atlas》,the recording electrode was inserted in right frontal lobe cortex and SB-271046or HP-β-CD was microinjected into LV in day28.4. Rats’spontaneous recurrent seizures(SSRs) were observed according to Veliskova and Goffin’s criteria and epileptic discharges were recorded by electroencephalography (EEG).5. Y-maze Spontaneous alternation behavior(SAB) test,Y-maze Novel object discrimination(NOD) test and Morris water maze(MWM) test were used to evaluate the rats’spatial learning-memory. 6. Rats were sacrificed after MWM and the brains were removed. The expression of5-HT6receptor in different tissues especially prefrontal cortex, hippocampus and striatum were observed and anlyized by immunohistochemisty and Western blot.Results1. Successful rate and survival rate of pilocarpine-induced epileptic model:In the first experiment, the successful rate and the survival rate were72.55%and37.84%. In the second experiment, the successful rate and the survival rate were85%and52.94%.2. Behavior changes in chronic period:Compared with the HP-CD group, the frequency of SSRs decreased in20ug-SB group(P<0.001),which was also observed in10ug-SB group,although P>0.05; besides compared with10ug-SB group,20ug-SB decreased more (P<0.001).3. EEG recordings:Except Vehicle group, other groups were all receorded sharp-spike-waves, spike-and-slow-wave complex and multiple spike-and-slow-wave complex in chronic period. Compared with HP-CD group, the amplitude of epileptic discharges decreased in20ug-SB group(P<0.001),which was also observe in10ug-SB group, although P<0.05; besides compared with10ug-SB group,20ug-SB group decreased more (P<0.001).4. Y-maze performance:In Y-maze spontaneous alternation behavior test (SAB), alternation rate of HP-CD group decreased significantly (P<0.01), SB-271046reversed the defect especially20ug doses (P<0.05); In Y-maze novel object discrimination4h ITI test, new arm percentage of HP-CD decreased significantly (P<0.01),SB-271046didn’t reverse the defect.5. Morris water maze (MWM) performance:In acquisition stage, the means latency of all groups were gradually shorten from day1to day5; Moreever, the5days mean latency of HP-CD was prolonged significantly (P<0.01),SB-271046reversed the defect especially20ug doses (P<0.05).In retention stage, the means latency, numbers of crossing target and percentage of performance time in target zone of HP-CD decreased,but SB-271046didn’t reverse the defects.6. Immunohistochemisty obsevertion:The positive cells of5-HT6receptor in different brian zones and in different groups were different (P<0.001). In Vehicle group, it was highly expressed in Striatum, moderately in Cortex and Hippocampus; In HP-CD group, it was highly expressed in Cortex, moderately in Hippocampus and Striatum; In10ug-SB and 20ug-SB groups, they were almost the same, moderately expressed in Cortex, Hippocampus and Striatum. What’s more,the toal positive5-HT6receptor cells of HP-CD groups were most,Vehicle group were least.20ug doses Of SB-271046could downregulate the level of5-HT6receptor (P<0.05). Besides, compared with lOug-SB group,20ug-SB decreased more (P<0.05).7. Western blot:The expression of5-HT6receptor in different brian zones and in different groups were different (P<0.001). In Vehicle group, it was highly expressed in Cortex and Hippocampus, moderately in Striatum; In HP-CD group, it was highly expressed in Cortex, moderately in Hippocampus and Striatum; In10ug-SB and20ug-SB groups,they were almost the same, moderately expressed in Striatum, Cortex and Hippocampus. What’s more,the toal5-HT6receptor of HP-CD group was most, Vehicle group was least.20ug doses SB-271046could downregulate the level of5-HT6receptor (P<0.05)Conclusions1.5-HT6receptor antagonist SB-271046reduced the frequency of chronic spontaneous seizures and the amplitude of epileptic dischages, expecially20ug doses SB-271046.2. The learning-memory of epileptic rats were impaired.5-HT6receptor antagonist SB-271046reversed epileptic rats’learning-memory defects, espacially in acquisition stage, expecially20ug doses SB-271046.3. The expression of5-HT6receptor in different brian zones and in different groups were different. The disposition5-HT6receptor of HP-CD group was different from Vehicle group, which might suggest the effects of SSRs. Moreever SB-271046could downregulate the level of5-HT6receptor, especially20ug doses.4. The effects of5-HT6receptor antagonist SB-271046on reduction the seizures of SSRs and improvement learning-memory of epileptic rats were might be through down-regulating the expression of5-HT6receptor.