IMMUNOHISTOCHEMICAL MAPPING OF PERINEURONAL NETS CONTAINING CHONDROITIN UNSULFATE PROTEOGLYCAN IN THE RAT CENTRAL-NERVOUS-SYSTEM

Subsets of neurons ensheathed by perineuronal nets containing chondroi tin unsulfate proteoglycan have been immunohistochemically mapped thro ughout the rat central nervous system from the olfactory bulb to the s pinal cord. A variable proportion of neurons were outlined by immunore activity for the monoclonal antibody (Mab 1B5), but only after chondro itinase ABC digestion. In forebrain cortical structures the only immun oreactive nets were around interneurons; in contrast, throughout the b rainstem and spinal cord a large proportion of projection neurons were surrounded by intense immunoreactivity. Immunoreactivity was ordinari ly found in the neuropil between neurons surrounded by an immunopositi ve net. By contrast, within the pyriform cortex the neuropil of the pl exiform layer was intensely immunoreactive even though no perineuronal net could be found. The presence of perineuronal nets could not be co rrelated with any single class of neurons; however a few functionally related groups (e.g., motor and motor-related structures: motor neuron s both in the spinal cord and in the efferent somatic nuclei of the br ainstem, deep cerebellar nuclei, vestibular nuclei; red nucleus, retic ular formation; central auditory pathway: ventral cochlear nucleus, tr apezoid body, superior olive, nucleus of the lateral lemniscus, inferi or colliculus, medial geniculate body) were the main components of the neuronal subpopulation displaying chondroitin unsulfate proteoglycans in the surrounding extracellular matrix. The immunodecorated neurons found in the present study and those shown by different monoclonal ant ibodies or by lectin cytochemisty, revealed consistent overlapping of their distribution patterns.