Anti-chondroitin unsulfated proteoglycan (COS-PG) 1B5 monoclonal antibody (MAb) and Vicia villosa agglutinin (VVA) recognize the same neuronal subset. Moreover, when in double immunofluorescence study the sections were digested with chondroitinase ABC (ChABC), a procedure necessary to create the epitope of 1B5 MAb, and incubated with VVA, no VVA positive neurons were detected. This finding suggests that VVA binds terminal N-acetyl-galactosamine present in the glycidic chains of COS-PG or of glycoproteins that form perineuronal molecular aggregates with COS-PG.