Histochemical localization of carbonic anhydrase in vertebrate nervous tissue.

The histochemical method of Häusler was employed to demonstrate carbonic anhydrase (CA, carbonate hydrolase, 4.2.1.1.) in tissue sections. The CA reaction was inhibited in the presence of 5 mM acetazolamide. In the frog and fish retinas the CA activity was positive in the Müller fiber, the laminated segment of the cones and the myelin of the axons, and was negative in the laminated segment of the rods, the photoreceptor ellipsoid and myoid, the horizontal, bipolar, amacrine and ganglion cells, and the pigment epithelium. In the spinal cord of cat and fish the CA activity was positive in the myelin of the axons, the perineuronal oligodendroglia and the protoplasmic astrocytes, and was negative in the cell body, dendrite, and axon of the neurons and in the fibrous astrocytes. In the dorsal root ganglion of the cat CA reaction was positive in the satellite cells and the myelin, and was negative in the neuronal cell body and its processes. The capillaries in central nervous tissue show no CA reaction. The erythrocyte is CA positive while the mitochondria are CA negative.