Intra- and extraneuronal monoamineoxidase-A and -B activities after central axotomy (hemisection) on rats.

Hemitransection of the left side of rat brain results in a selective increase (40%) in the activity of MAO-B in the left side striatum, as compared to the right, unoperated side. This increase is shown to be the result of an increase in the activity of extraneuronal MAO-B using a "low substrate concentration method" with dopamine as substrate. This result is compatible with the hypothesis, that in certain degenerative processes such as aging, Alzheimer's disease, Huntington's disease and axotomy there is a stimulated growth of extraneuronal cells, which are relatively rich in MAO-B activity.