Local cytochrome oxidase activity in the cerebral cortex of the rat, histochemically detected with the DAB-method: a micro-densitometric and electron microscope study.

For demonstration of the local cytochrome oxidase activity, coronal sections through the frontal cortex of four Sprague-Dawley rats were incubated with DAB medium after Seligman et al. (1968). The pattern of distribution of the DAB reaction product (DAB-RP) was measured at a wavelength of 460 nm. Cryostat sections were scanned with a microdensitometer. The cytochrome reaction product was accumulated in the laminae I and IV. A comparative morphometric study of mitochondrial profiles in ultra-thin sections through equivalent cortical regions showed an approximately similar distribution in percentage of areal density of the mitochondria labeled by DAB-RP. On average 30% of the mitochondrial profiles were labeled with DAB-RP which was localized in the intracristate spaces and the outer mitochondrial compartment. The marked mitochondria mainly occurred in dendrites. Furthermore, the mean and median value of the size distribution of marked mitochondrial profiles was shifted to greater values when compared with non-marked ones.