Acute Functional Recovery of Cerebral Blood Flow after Forebrain Ischemia in Rat

After complete cerebral ischemia, the postischemic blood flow response to functional activation is severely attenuated for several hours. However, little is known about the spatial and temporal extent of the blood flow response in the acute postischemic period after incomplete cerebral ischemia. To investigate the relative cerebral blood flow (rCBF) response in the somatosensory cortex of rat to controlled vibrissae stimulation after transient incomplete ischemia (15-min bilateral common carotid artery occlusion + hypotension), we employed laser speckle imaging combined with statistical parametric mapping. We found that the ischemic insult had a significant impact on the baseline blood flow (P <0.005) and the activation area in response to functional stimulation was significantly reduced after ischemia (P < 0.005). The maximum rCBF response in the activation area determined from the statistical analysis did not change significantly up to 3 h after ischemia (P > 0.1). However, the time when rCBF response reached its maximum was significantly delayed (P < 0.0001) from 2.4 ± 0.2 secs before ischemia to 3.6 ± 0.1 secs at 20 mins into reperfusion (P < 0.001); the delay was reduced gradually to 2.9 ± 0.2 secs after 3 h, which was still significantly greater than that observed before the insult (P = 0.04).