The Time Evolution of Cerebral Infarction in Rat Middle Cerebral Artery Occlusion

ABSTRACT

For the assessment of clinical management, for the confirmation of clinical findings, and also for the evaluation of new diagnostic techniques to determine the location as well as the extent of area of infarction on evolution in cerebral tissue is essential. Sequential evolution of infarction in 2% 2, 3, 5-triphenyltetrazolium hydrochloride(TTC) staining and its concomitant neurological changes were investigated in the rat following left middle cerebral artery occlusion(MCAO). In addition, the pathological evaluation was performed in the same coronal cut slice of each TTC staining. The results were: 1) In the TTC staining method, the cerebral infarction was not found in the 2 hour group rats, and appeared as white or pink color after 4 hours. 2) The size of infarction was significantly correlated with time of occlusion before sacrifice(p<0.05). The size increment was most obvious between 8 hour and 24 hour groups. 3) The time evolution of cerebral infarction was most prominent in the cerebral cortex, and was minimal in the basal ganglia which are supplied by the 'end artery'. 4) The cerebral infarction appeared first in the coronal cuts at the 4, 6, and 8mm from the frontal pole, which is the main territory of MCA. 5) The cerebral infarction, mainly presented in the 4, 6, and 8mm coronal cuts from the frontal pole, extended from the pyriform cortex to the fronto-parietal cortex. It also appeared at 2, 10mm coronal cuts from the frontal pole in 24 hour group. 6) The neurologic sign was not correlated to the time of MCAO and the size of infarction on evolution. Therefore, the prediction of location and size of area of infarction on evolution was impossible by the neurological status. 7) The histopathological change was detected as early as in 2 hours. However, hematoxylin and eosin(H & E) stained sections showed only subtle changes, such as small irregular areas of cortical spongiosis and neuronal shrinkage up to 8 hours. There was no significant difference between lesion areas of 2 hour and 8 hour groups. The pathological findings of 24 hour group rats was definite and appeared as a central area of coagulation necrosis and rarefaction surrounded by a zone of peripheral spongiosis.