Effect Of Muscone On Neuronal Glutamate Transporter Of Acute Cerebral Ischemia In Rat

Neuronal death after cerebral is determined by damage cascade including exitotoxicity, calcium over- loading, oxygen free radical expression, inflammation and so on. During cerebral ischemia, there is a rise in extracelluar cerebral glutamate content that activate glutamate- mediated channels to neurotoxic levels. Recent studies demonstrate that reversal of neural excitatory amino acid transporter(EAAC1) instead of uptake to be a principal cause for elevated extracellular glutamate levels that induce excitotoxity and inniate damage cascade. Therefore, anti-excitotoxity possesses the action of neuro -protection. Xingnaokaiqiao formula was wildly used in the early stage of cerebral ischemia. In this study , we observed whether Muscone could attenuate EAAC1 expression and reverse uptake during cerebral ischemia and participate in neuprotection .Further, the research would suggest a new clew for anti-excitotoxity. Methods Brain microinjection of neural excitatory amino acid transporter(EAAC1) antisense oligodeoxyneucleotide(EAAC1 antisense), TTC staining and western blot analysis were adopted for probing the effects of EAAC1 on the brain injury in rat model with MCAO. In order to study its neuroprotection,Muscone was given(1mg/kg b.w) by gavage before middle cerebral artery occlusion(MCAO) operation. At 24h after MCAO, brain tissues were taken by decapitation and infarction volumes were qualified by TTC staining. The change of ultrastructure with cerebral cortex were observed by electron microscope.Semi-quantitative analysis of RT-PCR and western blot analysis were used to detect EAAC1 mRNA and protein expression of EAAC1,GLT of different group. In order to study Muscone's neuroprotection mechanism, Semi-quantitative analysis of RT-PCR and western blot analysis were used to detect EAAC1 mRNA and protein expression of EAAC1,GLT ofdifferent group. At the same time,the effect of muscone (0.01% to 0.16%) on reversed uptake glutamate was examined.Results: After microinjection of EAAC1 antisense into the central area of cerebral ischemia , the expression of EAAC1 was nearly depressed (P<0.01)and the volume of brain ischemic infarct was reduced(P<0.01).Treatment with Muscone significantly reduced the infarction volume and ameliorate the damage of ultrastructure. RT-PCR and western blot analysis showed that EAAC1 mRNA expression began to increase gradually at 6hr(p<0.01) while protein expression was higher at 24hr only in hippocampus after MCAO(p<0.01) .Both EAAC1 mRNA in cerebral cortex and protein expression in hippocampus and cerebral were higher at 24hr only after MCAO(p<0.01). In the Muscone-treated rats , a marked reduction was shown in higher levels of EAAC1 mRNA levels and protein levels at different time after MCAO(p<0.05or p<0.01).Muscone at concentration 0.04% and 0.08%began to attenuate EAAC1 reverse uptake(p<0.01)while at concentration 0.16%, its action began to decreased(p<0.05). Conclution our data indicated that EAAC1 is related to brain damage during cerebral ischemia. Muscone could attenuate infarct volume and ameliorate the damage of ultrastructure with cerebral cortex, so it possesses the action of neuprotection. Moreover, the neuroprotection is possibly related to attenuate EAAC1 expression and reverse uptake during cerebral ischemia...