Histochemical mapping of the distribution of monoamine oxidase in the diencephalon and basal telencephalic centers of the brain of squirrel monkey (Saimiri sciureus)

The activity of monoamine oxidase (MAO) was mapped at the macroscopic level using 50 μ thick fresh frozen sections arranged in a caudo-cranial series of sections through the diencephalon and basal telencephalic centers of the squirrel monkey brain. The various thalamic nuclei show a mild MAO reaction except the nuclei periventricularis and para- and subfascicularis, which show moderate MAO reaction. The hypothalamus, in general, shows a stronger MAO reaction than the thalamus, because of its involvement in various autonomic functions. The nuclei paraventricularis, supraopticus and ventromedialis hypothalami are particularly prominent because of the stronger MAO activity they show in contrast to other hypothalamic areas. The nucleus caudatus, putamen and globus pallidus show mild to moderate MAO activity. The fiber bundles of fimbria hippocampi, fornix, anterior commissure and internal capsule show a moderate to moderately strong MAO reaction. The nuclei of the amygdaloid complex differ little from one another and show negligible to mild MAO activity. The nuclei dorsalis, medialis and lateralis septi show a mild MAO reaction compared to the moderate activity in the nuclei fasciculi diagonalis Brocae and triangularis septi.