Light microscopy of tissue sections stained with cationic iron colloid (pH 1.0-2.0) and nuclear fast red or with this colloid and thionin revealed the presence of numerous neurons with a strong negative-charge or coated with sulfated proteoglycans such as chondroitin sulfates in the adult rat brain. These neurons were distributed mainly in the hippocampal subiculum, zona incerta, cerebral cortex (V lamina), medical cerebellar nuclei and certain other nuclei such as ventral pontine nuclei. In the hippocampal formation, the strongly negatively-charged cells seemed to be identical with the GABAergic inhibitory interneurons reactive to the lectin Vicia villosa agglutinin. The neurons, including the GABAergic Purkinje's cells, of the cerebellar cortex showed no reaction to the cationic iron colloid at pH 1.0-2.0. Many non-GABAergic large neurons of the ventral pontine nuclei were well reactive to the colloid at pH 1.0-2.0. These findings suggest that the cationic iron colloid at pH 1.0-2.0 mainly stains some subsets of GABA-ergic neurons, and additionally stains some non-GABAergic interneurons projecting long association or commissural fibers.
Cationic iron colloid staining
central nervous system