Dynamics of ischaemic brain oedema fluid: 'dense tracer distribution around the focus', evaluated by peroxidase injection in the rat cortex.

Experimental cerebral ischaemia was produced by microembolization in rats. HRP (horseradish peroxidase) was then injected into the cerebral cortex and the extracellular fluid dynamics were observed. In the control group, there was a basic pattern in the migration of the tracer. In the ischaemic group, a 'dense tracer distribution around the focus' was found in addition to the basic pattern. This phenomenon could be observed from the second day after the ischaemic insults. The perivascular DAB reaction was marked, particularly around the focus. There was a vesicular uptake of the tracer in the vascular endothelium. This phenomenon appeared almost simultaneously with the active resolution of the oedema fluid. In addition, frequent mitotic figures were seen around the focus. It was thus possible to hypothesize that the 'dense tracer distribution around the focus' appeared at the site of active tissue reaction and had a close relationship with oedema resolution.