A note upon the striatal distribution of cytochrome oxidase activity in the rat and in the cat.

The distribution of cytochrome oxidase (CO) activity was explored in the striatum of two mammalian species, the rat and the cat. Regional differences in the striatal distribution of CO were detected in both species. Thus, in most of our experimental material for rodents, an extensive band richer in CO was present in peripheral regions of the rostral and outer part of the corpus striatum. This striatal band was running in coronal sections, from medial and dorsal to lateral and ventral. In the cat's striatum, rostral and, above all, dorsal territories of the caudate nucleus were prominently stained for CO. In addition, in both species, although more sharply shown in the cat, it was possible to delineate a heterogeneous distribution of this mitochondrial enzyme following the local compartmental design of acetylcholinesterase (AChE) within the mammalian striatum. Zones with low concentration of AChE were in register with areas in which CO was low as well. This regional and local striatal heterogeneity might be a consequence of differences in the mitochondrial activity of cells located in diverse histochemical striatal parcels and, therefore, with different functional targets outside the striatum.