OCCURRENCE OF A N-TERMINAL PROTEOLYTIC FRAGMENT OF NEUROCAN, NOT A C-TERMINAL HALF, IN A PERINEURONAL NET IN THE ADULT-RAT CEREBRUM

Neurocan is a nervous tissue-unique chondroitin sulfate proteoglycan ( CSPG) whose expression and proteolytic cleavage are developmentally re gulated. In the adult rat brain, neurocan is completely cleaved into s ome proteoglycan fragments including the C-terminal half known as neur ocan-C and a N-terminal fragment with a 130 kDa core glycoprotein (neu rocan-130). We describe here the differential distribution of these tw o neurocan-derived CSPGs in the adult rat cerebrum and the occurrence of neurocan-130 as a new member of a perineuronal net-constituting mol ecule. At the light microscopic level, neurocan-130 exhibited pericell ular localization around a subset of neurons in addition to diffuse di stribution in the neuropil. In contrast, neurocan-C was distributed on ly diffusely in the neuropil. Double staining with anti-neurocan-130 a nd anti-synaptophysin antibodies suggested that neurocan-130 was local ized in the vicinity of the synapses, but not at the synapses. Immunoe lectron microscopy showed that neurocan-130 was mainly localized in th e cytoplasm of glial cell processes, the so-called glial perineuronal net, encompassing the cell bodies of certain neurons. The presence of neurocan-130 in a limited number of glial cells may reflect some funct ional heterogeneity of the glia. (C) 1998 Elsevier Science B.V.