The Experimental Studies On Changes Of Neuroimaging And Amino Acids In The Early Stage Of Permanent Focal Cerebral Ischemia In Cats

Objectivel To establish a stable permanent focal ischemia model incats.2 To investigate the changes of metabolic rate of glucose,HMRS, and amino acids in different brain regions of catsfollowing permanent focal cerebral ischemia.Methodsl A permanent focal cerebral ischemia model of cat wasestablished by electrocoagulating the terminal of leftmiddle cerebral artery via a transorbital approach. Afterneurologic examination, the cats were killed for TTC andHE stain, and the volume of infarction were calculated.2 20min before or 30min, 3, 6, l2, 24,24hrs, and 7 daysafter ischemia, 0.5mCi ¹⁸FDG were intravenous bolusinjection. ^l8FDG-PET scans were made and the SUVs ofROIs were measured.3 l hr, 3, 6, 12, 24hrs, 2, 3,5, and 7 days following ischemia,T₁WI, T₂^*, T₂WI, DWI, and ^lHMRS were made.4 The changes of amino acids in ECF following ischemiawere detected by microdialysis and HPLC.Resultl This cat cerebral ischemia model could produce amoderate infarction distributing in Sylvian's gyri, head of7caudatum, and part of suprasylvian's gyrus. The averageinfart size was 2l .9 t l .23% of hemispheric area2 A picture of cat brain was obtained by l8FDG-PET..scanning via IV lsFDG after ischemia. 30min after MCAO,there was a lower radioactive trace in the left MCAdistribution area than in contralateral and control area.From 3hrs to l2hrs after ischemia the radioactive trace wasdecreased gradually in ischemic core, and the changestopped thereafter. Meanwhile, the radioactive trace in themarginal area increased gradually starting at 6hrs afterischemia and was equal to that of contralateral and controlarea 7days after ischemia. Comparing with contralateralside SUVs measured in ischemic area were significantdecreased at different time of ischemia, and it was mostprominent in ischemic core(p<0.0l ).The SUVs decreasedrapidly in the early stage of ischemia and then restoredgradually in the marginal area. And this change was notprominent in ischemic core.lsFDG was given intravenously 20mins before MCAO,lsFDG-PET scanning were performed at different time ofischemia. It was found that l0mins after MCAO the SUVwas higher than that of contralateral and control area;l 0mins to 3hrs after MCAO, the SUVs increased gradually.Then it decreased gradually and was equal to that of8contralateral area 6hrs after MCAO. There was a significantdense radioactive trace in the MCA distribution area thanthat of contralateral and control area(p<0.05) l 0min afterMCAO. The radioactive trace increased gradually andfocused on the core of ischemia. The dense area wascoincided with the former bright area.3 The ischemic regions could be identified by DWI lhr afterMCAO. The abnormal signal was much obvious 3hrs later.T,WI could not find the abnormal signal until 6hrs afterMCAO.lHMRS could detect a lactate peak in the ischemiccore immediately after MCAO. After a transient increasing,the peak decreased gradually and disappeared 24hrs afterischemia. But an unknown peak was found and it might be aninositol peak. NAA peak was decreased progressively in thecore area after ischemia. It was significantly decreased at6hrs, could be detected a little at l2hrs, and wasdisappeared completely at 24hrs after MCAO. The changesof lactate peak in penumbral area was similar to that inischemic core 6hrs after ischemia, but it cleared rapidlyl 2hrs later(p<0.05). NAA peak was diminished afterischemia in the penumbral area, but it was not disappeared,and the change was not obvious l 2hrs after ischemia.4 It was found that the EAAs and IAAs had a rapid increasein the ischemic core immediately after ischemia by9microdialysis and HPLC. The increase of EAAs was aboutl 0-fold(p<0 .0 l )immediately after ischemia, it persistedafterwards and reached the peak l 8hrs after ischemia, thenit had a slight decrease. The increase of IAAs was about6-fold...