Perineuronal sulfated proteoglycans in the adult rat brain: histochemical and electron microscopic studies.

Neurons of cerebellar nuclei in the rat brain had a marked surface coat which was stained with cationic iron colloid or aldehyde fuchsin. Neurons with a similar surface coat were also noted in the retrosplenial cortex. The surface coat was stained doubly with cationic iron colloid and aldehyde fuchsin. Digestion with hyaluronidase eliminated the stainability of the surface coat to both agents. Combined digestion with chondroitinase ABC, heparitinase and keratanase eliminated the cationic iron colloid staining but did not interfere with the aldehyde fuchsin staining. Electron microscopy of ultrathin sections revealed that the iron particles were deposited in the perineuronal tissue spaces. These findings indicate that the surface coat consists of sulfated proteoglycans which occupy, as the extracellular matrix, the perineuronal tissue spaces. Many neurons in the retrosplenial cortex were labeled with lectin Vicia villosa agglutinin. Double staining revealed that these lectin-labeled neurons are usually reactive to cationic iron colloid. Few neurons in the cerebellar nuclei were labeled with lectin V. villosa agglutinin.