Impact of mild hypothermia after ischemia/reperfusion on the cerebral blood perfusion of rats with chronic cerebral hypoperfusion

Abstract

This study aimed to investigate the impact of mild hypothermia on cerebral blood perfusion in rats with chronically hypoperfused brain. After ischemia/reperfusion, 12 male healthy Sprague Dawley (SD) rats were randomly divided into normal temperature group (group NT, n=6) and mild hypothermia group (group MH, n=6). The cerebral hypoperfusion model was successfully established by end-to-end anastomosis of the right common carotid artery and the right external jugular vein. After hypoperfusion for 6 weeks, blood perfusion restored, and rectal temperature was maintained at 37°C with a controllable incubation pad in the NT group, while the rectal temperature was maintained at 32°C in the MH group. Rats were re-warmed 3 h after reperfusion. Local cerebral blood perfusion (LCBP) was determined with a laser Doppler flow perfusion imager before reperfusion (T1), immediately after reperfusion (T2) and 48 h after reperfusion (T3). Rats were sacrificed 48 h after reperfusion to observe the ultramicrostructure of brain tissues under transmission electron microscope. In the MH group, LCBP was slightly decreased immediately after reperfusion, and LCBP 48 h after reperfusion restored to the baseline before reperfusion. However, LCBP was significantly decreased immediately and 48 h after reperfusion in the NT group, and the LCBP did not restore to the baseline before reperfusion. In both groups, brain cells at the reperfusion side were swollen, degenerated or even necrotic at different degrees, but the degree of brain damage was slighter in the MH group. The results indicate appropriate early-stage mild hypothermia which may reverse cerebral hypoperfusion and ischemia in rats withchronic cerebral hypoperfusion after reperfusion. Key words: Chronic cerebral hypoperfusion, mild hypothermia, laser Doppler flow perfusion imager.