Quantitative histochemistry of cytochrome oxidase in rat brain.

A quantitative analysis of cytochrome oxidase (CO) activity in histochemically stained sections of rat brain was developed using tissue standards and computerized image processing. Standards of brain paste containing known amounts of CO were cryosectioned and stained under the same conditions as brain sections. The gray levels of the stain were converted to units of CO activity using a calibration curve derived from densitometric analysis of the standards. The technique yields reproducible quantitative values, has the superior anatomical resolution of histochemistry, and is compatible with autoradiography.