Distribution of carbonic anhydrase activity in the rat central nervous system, as revealed by a new semipermeable...

Results obtained with a new method provided evidence for the extraneuronal localization of CA and supports the idea that the enzyme is very widespread in non-neuronal cell types of the CNS. Most of these cells were considered to be oligodendroglia, but probably the astrocytes also contributed to the reactivity of the neuropil. The perineuronal CA activity observed in the spinal cord, brainstem, cerebellum, and hippocampus could be astrocytic in origin. Our observations concerning the widespread CA staining of the CNS vessels pointed to the possible functional significance of CA in the vessel wall. This activity could be due not only to pericytes but also to astrocytic processes. We have not found stained myelin sheats although biochemically the myelin contained the enzyme. Might be that our histochemical reaction was not sensitive to the membrane bound form of the CA. The fact that the reaction of the nucleoli did not disappear after acetazolamide treatment could be explained on the basis of binding of the cobalt-phosphate complex to the proteins of the nucleolus.