Perineuronal nets are extracellular structures enwrapping the soma and proximal dendrites of some neurons known to be parvalbumin immunoreactive. The composition of the nets is not completely known, but it can change between different neurons. We studied the heterogeneous composition of a specific component of perineuronal nets, the signaling molecule Janusin (or Tenascin R), by means of a double immunofluorescence using lectin fromWisteria floribundaas a general marker for perineuronal nets and an antibody against Janusin. The presence of two kinds of perineuronal nets, one rich in Janusin (the majority) and a second one devoid of this glycoprotein, indicates differential roles of these neurons, as well as differences in their afferents, or a difference in their functional state.