The experiments were conducted on rats weighing from 200 to 250 g. Brain ischemia was reproduced by bilateral clipping of both common carotid arteries. We studied different parameters of brain microcirculation during the first hour after reperfusion.
The number of circulating (desquamated) endothelial cells by the method Hladovec described in 1978 was investigated. Research on the desquamated endothelial cells showed that at the end of the ischemic period and during the first 15 minutes after reperfusion begins their average quantity increased 2-fold in comparison with controls (9 cells/100?l and 4 cells/100?l correspondingly). After these periods their numbers decreased, but 60 minutes after reperfusion were still somewhat higher than in controls.
In addition, we studied brain microcirculation by brain scanning method with Tc-99m microspheres, injected via the carotid arteries after 5 minutes of reperfusion. In controls, labeled microspheres were accumulated only in the brain, and mostly in brain cortex and cerebellum. In experimental animals, microspheres were accumulated without border between brain cortex and cerebellum. In 50% of the experimental animals, microspheres were found not only in the brain but also in the lungs.
The activity of nitric oxide synthase was also researched by assessing NADPH-diaphorase activity in the brain vessels after 20 minutes of brain reperfusion. A slight increase of NADPH-diaphorase activity was found in the brain cortex vessels. But in the basal nuclei and hypothalamus, there were significant increases of NADPH-diaphorase activity in the large vessels compared to controls.
Conclusions:1. Brain ischemia and reperfusion causes an increase of endothelial cells desquamation.
2. During brain reperfusion, the opening of arterio-venous shunts occurs. Possible mechanisms are an increase of NO synthesis and increase of vessel diameters in the deep structures of the brain.
[Submission Form]