Investigation Of Validity And KCC2 Mechanism Of Cognitive Impairment In Rats Of Schizophrenia Model Induced By Repeatedly Treated With MK-801 In Perinatal Or Adult Period

PartⅠBehavioral test in schizophrenia model rats repeatedly treated with MK-801 during perinatal or adult periodObjective:Rats repeatedly treated with N-methyl-Daspartate (NMDA) antagonists have been thought to be a developmental and chronically treated model of schizophrenia(SZ) during perinatal period or adulthood.In this study,we investigated the face validity and related pathomechanism in two SZ model by the test and comparison of behavioral changes in SZ model rats.Methods:Neonatal male Spragur-Dawley(SD) rats were randomly assigned at the postnatal day 6 to three groups:SZ developmental animal model group(subcutaneous injection with MK-801 at the postnatal day 7-10,0.1 mg/kg Bid),SZ chronically treated animal model group(intraperitoneal injection with MK- 801 at the postnatal day 47-60,0.2 mg/kg Qd) and normal control group(injection with saline during the corresponding periods). Behavioral test were measured in three groups at the postnatal day 63, including Locomotion test,Forced Swimming test,Social Interaction test and Morris Water Maze test.Results:(1) In Locomotion test,the total path was significantly increased in SZ chronically treated model group compared with both SZ developmental and control groups;(P<0.01).(2) In Forced Swimming test,the immobility time was significantly increased in two model groups as compared with control group(P<0.05).(3) In Social Interaction test,the social behavior was significantly decreased in SZ developmental model group compared with both SZ chronically treated and control groups(P<0.05);the non-aggressive behavior percentage was significantly decreased in two model groups compared with control group(P<0.01).(4) In Morris Water Maze test,the escape latent period was significantly longer in two model groups than that in control group at the training day 3-4(P<0.01 or P<0.05);in memory retrieval test,the detention time in the target quadrant was significantly shorter in two model groups than that in normal control group at the day 5 (P<0.05).Conclusions:(1) SZ chronically treated model may be used to simulate partly positive symptoms in SZ.(2) Both two models could be used to simulate partly negative symptoms in SZ.(3) Both two models could be used to simulate partly cognitive impairment in SZ.(4) SZ developmental model repeatedly treated with MK-801 in perinatal period is the efficient supplement for SZ animal model treated with acute and chronic NMDA receptor blocking pharmacon in adult rats,and may refer to study of pathomechanism related to neurodevelopmental hypothesis in SZ.PartⅡComparison of the expression of PV,GAD67 and KCC2 in brain tissue in both SZ modelsObjectives:Rats repeatedly treated with NMDA antagonists (MK-801) have been thought to be a developmental and chronically treated model of schizophrenia(SZ) during perinatal or adult period.In this study,we investigated the construction validity and related pathomechanism in two SZ model by the comparison of pathological changes of Gamma-aminobutyric acid(GABA) system in SZ model rats.Methods:At the postnatal day 6,neonatal male SD rats were randomly assigned to two batches(B1 and B2) with each batch being randomly divided into three groups:SZ developmental animal model group (subcutaneous injection with MK-801 at the postnatal day 7-10,0.1 mg/kg Bid),SZ chronically treated model group(intraperitoneal injection with MK-801 at the postnatal day 47-60,0.2 mg/kg Qd) and normal control group(injection with saline during the corresponding periods).At the day P63,the brain tissues of B1 rats were fixed with paraform for histological section after decapitation.And then the expression level of parvalbumin(PV) and glutamate decarboxylase 67(GAD67) in the tissue homogenate from medial prefrontal cortex(mPFC) and hippocampus CA1 region was examined by immunohisto-chemistry technique.The tissue homogenates of mPFC and hippocampus were obtained for measuring the expression levels of K~+-Cl~- cotransporter 2(KCC2) in both brain regions in B2 rats with Western blotting.Results:(1) The expression level of PV and GAD67 in the mPFC and hippocampus CA1 region in both SZ model groups was significantly decreased compared with control group(P<0.01;P<0.05,respectivelly).(2) The expression level of KCC2 in the mPFC and hippocampus CA1 region in SZ developmental model group was significantly decreased compared with both SZ chronically treated model and control groups(P<0.05). Conclusions:(1) Both SZ models may be used to simulate partly pathological changes of GABA system in SZ.(2) In SZ developmental model group,the KCC2 expression was downregulated in some brain regions.(3) Both SZ models show certain construction validity and could be used to pathomechanism study related to SZ.PartⅢComparison of concentration of DA,Glu and their metabolism production in brain tissue in both SZ models repeatedly treated with MK-801Objectives:We explored the construction validity and its related pathomechanism by the comparison of concentration of dopamine(DA), glutamate(Glu) and their metabolism production,dihydroxy-phenyl acetic acid(DOPAC) and GABA in brain tissue in both SZ model rats. Methods:The treated measures for SD rats was similar to that in PartⅠ. After decapitation at the day P63,DA,DOPAC,Glu and GABA of the tissue homogenate from the medial prefrontal cortex(mPFC) and hippocampus were examined with Coularray Electrochemic detection for high performance liquid chromatogram(HPLC) technique.Meanwhile, the utilization rate of DA and Glu was calculated.Results:(1) The concentration of DA and DOPAC in both mPFC and hippocampus regions was significantly decreased in SZ developmental model group compared with control group(P<0.01).The DOPAC concentration and DA utilization rate in the mPFC were significantly decreased in SZ chronically treated model and DA utilization rated was increased in the hippocampus region compared with control group(P<0.05).(2) The DOPAC concentration and DA utilization rate in the hippocampus region was significantly decreased in SZ developmental model group compared with SZ chronically treated model group(P<0.01;P<0.05,respectivelly). (3) Compared with control group,the Glu utilization rate in the mPFC was significantly decreased in SZ developmental model group,and the GABA concentration and Glu utilization rate in the mPFC and Glu concentration in the hippocampus were significantly decreased in SZ chronically treated model group(P<0.05).Conclusions:(1) The activity of DA system in mPFC was decreased in both SZ models.(2) The activity of hippocampus DA system was decreased in SZ developmental model rats,while the activity of hippocampus DA system was increased in SZ chronically treated model group.(3) The activity of Glu and GABA systems in the mPFC was decreased in both SZ model groups.(4) The activity of hippocampus Glu system was decreased in SZ chronically treated model group.PartⅣStudy of the impairment of LTP in hippocampal slice and mechanism of KCC2 down-regulation after maturation in SZ developmental model ratsObjective:Perinatal repeated MK-801-induced developmental animal models of schizophrenia were employed to detect LTP change and KCC2 expression on the same fEPSP record region,and discussed the role of KCC2 in cognitive impairment of Schizophrenia.Methods:Pups on postnatal day 6(P6) were randomly assigned to two groups:SZ developmental model group(MK-801) and control group.SZ developmental model was developed by the same method as that in Part Ⅰ.Hippocampus slice was obtained on P61 immediately after rats were sacrificed by decapitation.The slice for electrophysiological recording was divided into four groups according to differential slice(MK-801 or Control) and perfusion drugs(FURO or PTX):Control group,MK-801 group,MK-801+FURO group and MK-801+PTX group.The experimental results were recorded by employing the field potential in hippocampus CA1 region.Study the influence of KCC2 inhibitor Furosemide(FURO) and GABA_A receptor antagonist Picrotoxin(PTX) on theta burst stimulation(TBS) -induced LTP.Western Blotting was used to detect changes of KCC2 expression on hippocampus CA1 after LTP induction.Results:(1) 40 minutes after TBS stimulation,the normalized fEPSP slope in hippocampal slice(105±3%) was significantly lower in SZ developmental model group than that in control period(149±2%)(P<0.05).(2) The fEPSP slope(130±2%) was significantly increased after perfusion of FURO in MK-801+FURO group compared with MK-801 group(P<0.05).(3) The fEPSP slope was significantly increased after perfusion of PTX in MK-801+PTX group compared with MK-801 group(146±2%) but no significant difference compared with control group(P>0.05).(4) Before LTP induction,KCC2 expression in hippocampal CA1 region was significantly decreased in MK-801 group compared with control group;following LTP induction, no significant change of KCC2 expression in MK-801 group compared with that before LTP induction,while it was significantly decreased in control group compared with that before LTP induction.Conclusions:(1) Perinatal Repeated treatment of MKS01 will lead to impairment of hippocampal synaptic plasticity of matured rats;(2) Perinatal Repeated treatment of MKS01 will inhibit the down-regulation of KCC2 during LTP expression after maturation,which caused the disturbance of GABA inhibition.(3) KCC2 may be involved in cognitive impairment mediated by the function down-regulation of NMDA receptor.