Regional Cerebral Blood Flow After Controlled Cortical Impact Injury in Rats

Regional cerebral blood flow (rCBF) and laser-Doppler perfusion were measured in rats after controlled cortical impact injury (CCII), a model of traumatic brain injury. Male Long-Evans rats were anesthetized with isoflurane and surgically prepared with arterial and venous cannulae. CCII was induced after a craniectomy by deforming the right parietal cortex to a depth of 2 mm with a metal cylinder traveling at a velocity of 5.2 m/s. Laser-Doppler perfusion was monitored from the surface of the left frontal cortex. rCBF, using 14C-isopropyliodoamphetamine, and laser-Doppler perfusion were measured in three groups of rats consisting of a sham group (n = 6), a group 30 min after CCII (n = 6), and a group 4 h after CCII (n = 5). CCII was characterized by cortical ischemia (rCBF < 20 mL.100 g-1.min-1) surrounding the site of impact. The occipital cortex, a cortical region distant from the impact site, was also ischemic in some, but not all, injured rats. In the 30-min group, the ischemic zone showed very sharp boundaries with cortical areas of hyperperfusion surrounding the ischemic zone. In the 4-h group, the ischemic boundaries were not as sharp and the hyperperfusion surrounding the ischemic zone was no longer present. The caudate-putamen, hippocampus, and thalamus showed significant reductions in rCBF ranging from 50% to 30% of control 30 min and 4 h postinjury, respectively. We conclude that complex changes in rCBF occur shortly after CCII and persist for at least 4 h. During this time several brain regions, especially the cortical areas, may suffer damage due to the ischemia.