The Effect Of Licl On The Expressions Of Tau Phosphorylation In Rats Ipsilateral Thalamus And Substantia Nigra After Cerebral Cortex Infarction

At present,the main therapetic measure for treating cerebral infarction is dissollving thrombus and restoring blood flow in order to rescue neurons which are still alive in the penumbra at early stage on the base of organized treatment mode.Thus,the neural impairment after cerebral infarction is lessened.Experimental investigation of cerebral infarction mainly focused on the infarction areas and the boundary around infarction areas.However,little investigation related to the secondary damage and neural plasticity of areas remote form infarction.Many animal experiment showed the permanent occlusion of unilateral middle cerebral artery in rats not only caused infarction in ipsilateral cerebral cortex,caudate nucleus and putamen,but also secondary degeneration in the ventroposterior nucleus of the thalamus(VPN) and the substantia nigra pars reticulata(SNR).The research have manifested the secondary damage following cerebral infarction may relate to axonal retrograde.Animal and clinical experiments indicate that lithium salt can be used to treat acute cerebral insult(ischemic and so on) and chronicity neuro-degenerative disease-(Alzheimer's disease,Parkinson disease,tauopathies and so on)in recent years.Tau proteins are mainly expressed in neurons where they play major regulatory roles in the organization and iniegrity of the cytoskeleton network.They promote microtubule cytoskeleton network.They promote microtubule stability and assembly,mainiain their structural integrity and promote axonal transport.Their cellular functions are mainly influenced by phosphorylation.,GSK-3βwas one of the most drastic kinase to phosphorylate tau.GSK-3βcan phosphorylate tau at ser199,ser396 and some other sites. Lithium salt had effect on GSK-3 through many ways to protect nervous system. Therefore the intervention measurement on tau protein may be the therapertic target to the secondary damage following cerebral infarction.Objective The aim of this work was to observe the secondary axon damage of homonymy ipsilateral thalamus and substantia nigra after cerebral infarction in hypertensive rats.In the same time,to investigate the influence of LiCl to axon damage of homonymy ipsilateral thalamus and substantia nigra and tau protein phosphorylation after cerebral cortex infarction in hypertensive rats.Methods1.Animal model and groupStroke-prone renovascular hypertensive rats were randomly divided into two groups:Sham operation group and right middle cerebral artery cortex occlusion(MCA O).The model of MCAO was successfully duplicated with electric coagulation.Groups: (1)Sham group,(2)MCAO group,(3)LiCl low-dose group(1.5mmol/kg),(4)LiCl high-dose group(3mmol/kg),every group have six rats.The LiCl low-dose group and LiCl high-dose group revecied i.p.injections of 1.5mmol/kg,3mmol/kg LiCl 24h postop,then once per 24h for two weeks until sacrificed.The MCAO group and Sham group revecied i.p.inject the same volume of Nacl injection instead of LiCl.2.Observation on experimental animal's behavior3.TTC staining2 rats taken from Sham group and MCAO group at postop 24h were randomly decapitated and the coronal brain slices were stained with TTC solution.The samples were postfixed and taken pictures.4.The brain slices from different groups were stained with HE solution.5.Bielschowsky method were used to stained the brain slices of different groups.6.Nissl stainingNissl staining was used to count the number of neurons in the ventroposterior nucleus of thalamus substantia nigra parsreticulata.7.Immunohistochemistry of phosphorylated tau(ser396)and tau-5.Results 1.Observation on experimental animal's behaviorThere were no neurological deficit in Sham-operated rats.The MCAO group,LiCl 1.5 group and LiCl 3.0 group had neurological deficit,and mainly focused on the paralysis of left foelimb.The functional score results:the functional scores of MCAO group,LiCl 1.5 group and LiCl 3.0 group was lower than that of Sham group(p＜0.05).2.Results of TTC stainingThe brain tissues were coloured cardinal red and no cortex infarction of Sham group.The brain tissues of MCAO group had no colour and there was an apparent stable infarction in right middle cerebral artery area.3.Calculate the volume of cerebral infarctionSham operation rats had no infraction area with Hestaining.The MCAO group, LiCl 1.5group and LiCl 3.0 group rats had one infarction area in the right cerebral motor sensory cortex Compared with the MCAO group,the volumes of infarction of LiCl 1.5 group and LiCl 3.0 group were decresed(p＜0.05).4.Silver staining-histopathological observationSham group had complete nerve fiber bundle in VPN and SNR with silver staining.The nerve fiber bundle of MCAO group:some of them was accumulation,some of others was lost.There are also some inequality of size irregular vacuolus-from structure in the non- complete nerve fiber bundle.The nerve fiber bundle of LiCl 1.5 group and LiCl 3.0 group was improved by LiCl treatment.5.Nissl staining-neurons countingThere were some isehemic changes and the norma neurons reduced of ipsilateral VPN and SNR in different groups.The morphology of neuron were improved in LiCl 1.5 group and LiCl 3.0 group compared to MCAO group.6.Immunohistochemical analysis of p-tau(ser396) and tau-5There was some expression of p-tau in Sham group,and it apparently increased in MCAO group(p＜0.05).Compared with MCAO group,the expression of p-tau(ser396) LiCl 1.5 group and LiCl 3.0 group were obviously decreased.The OD of tau-5 positive products was higher in MCAO group than that in Sham group(p＜0.05).It decreased in LiCl 1.5 group and LiCl 3.0 group compared with MC- AO group(p＜0.05).Conclusions1.The morphology of the cell in ipsilateral thalamus and substantia nigra were changed.Secondary axon anaplasia and tau was hyperphosphorylated also happen in ipsilateral thalamus and substantia nigra after cerebral cortex infaction for two weeks.2.LiCl salt ameliorate the morphology of neurons in ipsilateral thalamus and substantia nigra after cerebral cortex infaction and reduced the phosphorylation of tau.3.Tau protein is probably new targets of the research in recovering the neuronal function and the secondary damage of cerebral cortex infaction therapy.