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The aim of the study was to better understand blood-flow changes in large arteries and microvessels during the first 15 minutes of reflow in a P7 rat model of arterial occlusion. Blood-flow changes were monitored by using ultrasound imaging with sequential Doppler recordings in internal carotid arteries (ICAs) and basilar trunk. Relative cerebral blood flow (rCBF) changes were obtained by using laser speckle Doppler monitoring. Tissue perfusion was measured with [14C]-iodoantipyrine autoradiography. Cerebral energy metabolism was evaluated by mitochondrial oxygen consumption. Gradual increase in mean blood-flow velocities illustrated a gradual perfusion during early reflow in both ICAs. On ischemia, the middle cerebral artery (MCA) territory presented a residual perfusion, whereas the caudal territory remained normally perfused. On reflow, speckle images showed a caudorostral propagation of reperfusion through anastomotic connections, and a reduced perfusion in the MCA territory. Autoradiography highlighted the caudorostral gradient, and persistent perfusion in ventral and medial regions. These blood-flow changes were accompanied by mitochondrial respiration impairment in the ipsilateral cortex. Collectively, these data indicate the presence of a primary collateral pathway through the circle of Willis, providing an immediate diversion of blood flow toward ischemic regions, and secondary efficient cortical anastomoses in the immature rat brain. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the functional repercussions of cerebrovascular abnormalities in transgenic mice overexpressing TGF-β1. These mice develop Alzheimer''s disease-like vascular and meningeal alterations without parenchymal degeneration. Autoradiographic cerebral blood flow measurements in 9-month-old TGF-β1 mice compared to nontransgenic littermates provided evidence of reduced tissue perfusion, most prominent in limbic regions. A highly significant inverse correlation was found between the density of thioflavin-S-positive blood vessels and blood flow in the hippocampus and the cortex. An inverse correlation was likewise found between meningeal staining and blood flow in thalamic nuclei and regions of high blood flow. Thus, the vascular abnormalities were associated locally with reduced perfusion rate and more widely with limitation in the blood flow. These chronic changes may be related to fibrillar and soluble Aβ peptides, the amount of which was almost doubled in the brains of TGF-β1 mice. Comparison with previous results of cerebral glucose utilization in TGF-β1 mice shows that reduced utilization preferentially occurred in regions with a high metabolic rate and a relatively low blood flow, suggesting that the metabolic needs are not met by blood supply in these regions. [Copyright &y& Elsevier]