Histochemical study of the distribution of carbonic anhydrase in the cat brain.

The distribution of carbonic anhydrase (CA) in cerebrum, cerebellum and medulla oblongata of the cat brain has been examined by a histochemical method. Neuron cell bodies and dendrites are stained in some locations. Many axons are distinctly stained and different intensities of staining can be seen even in adjacent axons. One of the most intensely stained structures is the capillary endothelium and stained capillaries are found in all parts examined. Glial cells are intensely stained in agreement with biochemical and earlier histochemical works. Myelin sheaths are never stained, possibly due to enzyme loss during embedding. The localization of the enzyme shows regional differences. In this respect, the medulla oblongata has been examined in more detail. A small area close to the ventral surface, medial to the roots of the hypoglossal nerve, is characterized by a high CA staining of the neuropil. The cell membrane of some large neurones and the capillary endothelium in this area were also stained. With regard to position and CA content, this area corresponds well to the characteristics of the medullary chemosensitive area as defined by previous experimental studies.