This study was aimed at evaluating the regional changes in the cerebral metabolic rate of oxygen (CMRO2) in relation to the cerebral blood flow (CBF) in the bilateral common carotid artery occlusion (BCAO) rat model. Ligation of the bilateral common carotid arteries (or a sham operation in control animals) was performed in 10-week-old male Wistar rats. O-15 PET images were acquired in the subacute phase (1 week after the surgery) and chronic phase (6 weeks after the surgery) with the animals under anesthesia, using a small-animal PET system and the O-15 gas steady-state inhalation method with arterial blood sampling developed in our previous study. Histopathological staining by Klüver-Barrera method and immunocytochemistry staining by glial fibrillary acidic protein were performed. Cognitive function was tested by using the apparatus of Y-maze. Significantly lower CBF and higher oxygen extraction fraction were observed in broad areas of the cerebrum in the subacute phase in the BCAO rats, with recovery in the chronic phase. A stable decrease of the CMRO2 in the subacute phase of arterial occlusion and later was observed in the BCAO rat model, mainly in the anterior cerebral artery territory. Atrophy and rarefaction of corpus callosum were found in the BCAO in the chronic phase. Activity of astrocytes in the BCAO was prominent in the both phases. Working memory was impaired in the BCAO in the chronic phase. Regional changes in cerebral perfusion and oxygen metabolism in the subacute and chronic phases of arterial occlusion were clarified in a rat model of BCAO by quantitative O-15 PET based on the steady-state method.
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