Sequential cerebral blood flow changes in short-term cerebral ischemia in gerbils.

Using quantitative autoradiography, we studied sequential changes in regional cerebral blood flow during and after 2 minutes of bilateral common carotid artery occlusions in 18 gerbils. Occlusion (n = 4) led to severe ischemia in the forebrain (regional cerebral blood flow less than 5% of control [n = 4]) and midbrain (regional cerebral blood flow less than 10% of control), but was morphologically nonlethal. Reperfusion of the brain was complete, and regional cerebral blood flow was not different from control 1 minute after ischemia (n = 4), but hypoperfusion (regional cerebral blood flow 30-50% of control) occurred at 5 minutes (n = 3) and was pronounced at 1 hour (n = 4); at this stage blood flow was inhomogeneous. Hypoperfusion had disappeared at 4 hours (n = 3). Our results indicate that the well-documented sequence of cerebral blood flow changes (i.e., ischemia, initial recovery of blood flow, and delayed hypoperfusion) takes place even after nonlethal cerebral ischemia.