Perineuronal sulfated proteoglycans, cell surface glycoproteins and dark neurons in the cingulate cortex of newborn and adult rats.

Many neurons in the adult rat cingulate cortex possess perineuronal sulfated proteoglycans detectable with cationic iron colloid and aldehyde fuchsin, or cell surface glycoproteins reactive to lectin Vicia villosa or soybean agglutinin. The perineuronal sulfated proteoglycans develop three to four weeks after birth. The cell surface glycoproteins develop at earlier stage or two to three weeks after birth. Dark or active neurons begin to appear three to four weeks after birth. These findings indicate that the brain matures after birth or during weaning period.