Neuronal carbonic anhydrase activity in the central nervous system of the rat: light- and electron histochemical investigations of the islands of Calleja.

Results obtained with a new semipermeable method provided evidence for the neuronal localization of carbonic anhydrase in the olfactory tubercle of the rat brain. Examination of serial coronal sections revealed the carbonic anhydrase content of the granule cells in the islands of Calleja. The enzyme was localized in the nucleus and the cytoplasm of these neurons and did not show binding to any of the intracellular organelles. The large neurons of the olfactory tubercle did not contain the enzyme. The enzyme activity of the granule cells was totally abolished by 10(-4) mol/l acetazolamide. Since, up to now, carbonic anhydrase activity has not been demonstrated with histochemical techniques in any central neurons, our results are the first indication of the presence of this enzyme in mammalian central neurons.