Neurons of the retrosplenial cortex, hippocampal subiculum, pontine nuclei, intracerebellar nuclei and some other nuclei in the mouse demonstrated a marked surface coat which was formed three or four weeks after birth. This coat was stained doubly with cationic iron colloid (pH 1.0-1.5) and aldehyde fuchsin or with alcian blue and aldehyde fuchsin. Digestion with hyaluronidase eliminated all the cationic iron colloid, aldehyde fuchsin and alcian blue stainings of the surface coat. Successive digestion with chondroitinase ABC, heparitinase and keratanase erased the cationic iron colloid and alcian blue stainings of the surface coat, but did not interfere with the aldehyde fuchsin staining of this coat. Electron microscopy of ultrathin sections revealed that the iron particles were preferentially deposited in the perineuronal tissue spaces. These findings indicate that the surface coat consists of sulfated proteoglycans, which form an extracellular matrix in the perineuronal tissue spaces and as a charge barrier assure stable signal transmission at the axosomatic synapes with inhibitory nature. It was further observed that the neurons with such surface coats in the retrosplenial cortex and hippocampal subiculum were labeled with lectin Vicia villosa agglutinin.
Central nervous system
strongly negatively charged extracellular matrix