Histochemical mapping of succinic dehydrogenase and cytochrome oxidase in the diencephalon and basal telencephalic centers of the brain of squirrel monkey (Saimiri sciureus)

Summary The distribution of succinic dehydrogenase (SDA) and cytochrome oxidase (Cy. O) was mapped in the various diencephalic nuclei and basal telencephalic centers of the squirrel monkey brain. Thirty thick formaldehyde fixed serial sections were also studied for the delineation of the various nuclei, but histochemical preparations proved equally useful for this purpose. Strong SDA and Cy. O activity were observed in the habenular, pulvinaris, anterior dorsalis and ventralis, lateralis dorsalis and posterior, and ventral posterior nuclei. The corpus geniculatum laterale and mediale also showed a strong reaction for these enzymes. The nucleus ventralis anterior, which occupies a very large area in the rostral part of the thalamus, showed moderately strong activity in the cellular patches and negligible activity in the thick fiber bundles passing through it. A comparatively weak reaction was observed in the midline thalamic nuclei. The nucleus caudatus and putamen, however, showed very strong SDA/Cy. O activity. The hypothalamic nuclei showed mild Cy. O and moderate SDA reactions, except for the nucleus ventromedialis hypothalami. The latter showed a little stronger enzyme reaction. The fibers of the internal capsule and the anterior commissure showed little SDA and mild Cy. O activity. The various nuclei of the amygdaloid complex showed similar histochemical reactions with moderate SDA and mild Cy. O activity.This work has been carried out with the aid of Grant No. 00165 from the Animal Resources Branch, National Institutes of Health, and a grant from the National Foundation for Neuro-Muscular Diseases and Nasa Grant NGR-11-001-016.