An unanesthetized cat model of acute focal cerebral ischemia has been establishes by the technique of transorbital snare ligature for middle cerebral artery (MCA) occlusion, The model was used to investigate patterns of changes of regional cerebral blood flow (rCBF) for up to 16 hours following MCA occlusion by the hydrogen clearance technique and to explore the correlation among microregional blood flow changes, neurological deficit, and pathological changes including size of infarct and severity of brain edema. The animals were divided into 2 groups according to size of infarct that was identified by 2% triphenyl tetrazolium chloride solution stain. The results were as follows : 1) Infarct larger than 10% of coronal section surface of the ipsilateral cerebral hemisphere was found in 18 cats( Group A), and smaller infarct was found in the remaining 7 cats (Group B). Between these 2 groups, there was a statistically significant difference in the average rCBF value of ipsilateral MCA territory during 16 hours of ischemia (Group A:6.5ml/100g/min, Group B:32.6ml/100g/min) (P<0.01). 2) Increasing grade of contralateral paralysis correlated well with decreasing rCBF in MCA territory of occlusion side and all animals showing complete paralysis belonged to Group A with their average rCBF from ipsilateral MCA territory below 10.0ml/100g/min. 3) Increasing grade of cerebral hemispheric swelling was directly proportional to increasing grade of paralysis and there was also a significant difference in hemispheric swelling between Group A and B, Correlation between grades of infarct size and severity of paralysis was not evident. 4) There patterns of charges of rCBF were observed :In 15 cats of Pattern I, MCA occlusion caused persistent severe ischemia, measuring less than 16-17ml/100g/min(average rCBF:6.28ml/100g/min), to produce large infarct, pronounced paralysis, and severe histological damage(Group A). 5) In 7 cats of Pattern I, persistent mild to moderate ischemia, maintaining more than 23-24ml/100g/min(average rCBF:32.6ml/100g/min), was noted in association with much smaller infarct and milder hemiparesis(Group B). 6) In the remaining 3 cats of Pattern I, MCA occlusion caused immediate severe ischemia followed by early postischemic hyperemia and death during 8 to 14 hours after MCA occlusion owing to marked brain swelling and transtentorial herniation (Group A). 7) During the initial stage of ischemia, significant decrease in rCBF of the contralateral hemisphere was observed in both groups, however, in Group A, rCBF gradually increased to preocclusion level. Only Group B presented further decrease in rCBF suggesting the presence of interhemispheric diaschisis. Thus Group B appeared to take advantage of diaschisis during the late phase of infarct development as well as substantial collateral flow from the surrounding posterior cerebral and anterior cerebral artery territories.
Animals ; Anterior Cerebral Artery ; Brain Edema ; Brain Ischemia ; Cats ; Cerebral Infarction* ; Cerebrum ; Hydrogen ; Hyperemia ; Infarction, Middle Cerebral Artery* ; Ischemia ; Ligation ; Middle Cerebral Artery* ; Paralysis ; SNARE Proteins