The perineuronal proteoglycan surface coat in the adult rat brain, with special reference to its reactions to Gomori's ammoniacal silver

The present study showed that many neurons in the adult rat brain possessed a perineuronal sulfated proteoglycan surface coat which reacted to cationi c iron colloid and aldehyde fuchsin. This surface coat was stained supravit ally with Ehrlich's methylene blue and doubly stained with Ehrlich's methyl ene blue and aldehyde fuchsin. The surface coat was also stained with Gomor i's ammoniacal silver and doubly stained with Gomori's ammoniacal silver an d cationic iron colloid. The surface coat was usually expressed together wi th a nerve cell surface glycoprotein net detectable with lectin Wisteria fl oribunda agglutinin. These findings indicate that the perineuronal proteogl ycan surface coat is identical to Cajal's superficial reticulum and contain s some collagenous elements. It was further demonstrated that collagenase d igestion erased Gomori's ammoniacal silver impregnation within the perineur onal proteoglycan surface coat.