Uptake of macromolecules into neurons from a focal vasogenic cerebral edema and subsequent axonal spread to other brain regions. A preliminary study in the mouse with horseradish peroxidase as a tracer.

Intravenously (i.v.) injected horseradish peroxidase (HRP) which has leaked out of the vessels in a cryogenic cortical injury of adult mice is taken up into a large number of neurons resulting in two different forms of labeling. Diffuse neuronal labeling of the type previously reported in many conditions with vasogenic brain edema occurred particularly within the primary lesion. The other and more frequent type, here called granular neuronal labeling, was present in a wide zone immediately outside the injury. Such neurons contained HRP in numerous cytoplasmic granules and had the same characteristics as normal neurons accumulating HRP after retrograde axonal transport. By using highly sensitive histochemical methods for demonstration of HRP we could also follow bundles of labeled axons out from the primary lesion. Some of them passed the corpus callosum to the fronto-parietal cortex of the contralateral hemisphere. With this report we would like to put emphasize on certain phenomena occurring in neurons which previously have not been particularly recognized in studies on vasogenic brain edema. It can be assumed that in a focal brain lesion components from the edematous fluid and other "would substances" can be taken up into nerve cell processes and then be intracellularly transported in different directions. In this way, nerve cell populations located in other brain areas and even in the contralateral hemisphere may be influenced by components from the primary injury.