140518.836 052420.250 161815.729 131520.710 140521.520 131520.781 030518.300 091313.875 131514.660 012104.500 180520.029 180120*429 Immunohistochemical mapping of perineuronal nets containing chondroitin unsulfate proteoglycan in the rat central nervous system A. Bertolotto 1 , E. Manzardo 1 , R. Guglielmone 2 1 Centro Sclerosi Multipla, Divisione Universitaria di Neurologia, Università di Torino, Torino, Italy 2 Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Ospedale S. Luigi Gonzaga, Regione Gonzole 10, I-10043 Orbassano-Torino, Italy &misc:Received: 13 March 1995 / Accepted: 27 September 1995 &p.1:Abstract. Subsets of neurons ensheathed by perineuro- nal nets containing chondroitin unsulfate proteoglycan have been immunohistochemically mapped throughout the rat central nervous system from the olfactory bulb to the spinal cord. A variable proportion of neurons were outlined by immunoreactivity for the monoclonal anti- body (Mab 1B5), but only after chondroitinase ABC di- gestion. In forebrain cortical structures the only immu- noreactive nets were around interneurons; in contrast, throughout the brainstem and spinal cord a large propor- tion of projection neurons were surrounded by intense immunoreactivity. Immunoreactivity was ordinarily found in the neuropil between neurons surrounded by an immunopositive net. By contrast, within the pyriform cortex the neuropil of the plexiform layer was intensely immunoreactive even though no perineuronal net could be found. The presence of perineuronal nets could not be correlated with any single class of neurons; however a few functionally related groups (e.g., motor and motor- related structures: motor neurons both in the spinal cord and in the efferent somatic nuclei of the brainstem, deep cerebellar nuclei, vestibular nuclei; red nucleus, reticular formation; central auditory pathway: ventral cochlear nucleus, trapezoid body, superior olive, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body) were the main components of the neuronal sub- population displaying chondroitin unsulfate proteogly- cans in the surrounding extracellular matrix. The im- munodecorated neurons found in the present study and those shown by different monoclonal antibodies or by lectin cytochemisty, revealed consistent overlapping of their distribution patterns. &kwd:Key words: Central nervous system – Perineuronal nets – Extracellular matrix – Chondroitin unsulfate proteo- glycan – Immunohistochemistry – Rat (Sprague Dawley) Introduction The morphological variety of neurons in the central ner- vous system (CNS) has long been examined in detail by classical Golgi studies (see Valverde 1961; Ramon-Mo- liner 1962). The analysis of neuronal heterogeneity now takes advantage of the histochemical and immunocyto- chemical methods of chemical neuroanatomy: different sets of neurons can be classified according to the trans- mitters and/or neuropeptides they synthesize (Hökfelt et al. 1984). Recently, several immunocytochemical and lectin- binding studies have revealed that the extracellular ma- trix surrounding neurons is not uniform throughout the CNS, and that distinct subsets of neurons are coated by different glycoconjugates: by chondroitin proteoglycans (McKay and Hockfield 1982; Hockfield and McKay 1983; Kalb and Hockfield 1988, 1990a, 1990b; Sur et al. 1988; Watanabe et al. 1989; Fujita et al. 1989; Zaremba et al. 1989, 1990; Bertolotto et al. 1990, 1991; Bignami et al. 1992), by glycoproteins (Arimatsu et al. 1987; Naegele et al. 1988; Stephenson and Kushner 1988; Hin- ton et al. 1988; Kosaka et al. 1990), and by as yet un- identified lectin-binding molecules (Nakagawa et al. 1986a, b; Seeger et al. 1994). As has recently been em- phasized (Celio and Blümcke 1994; Härtig et al. 1994), there is a striking resemblance between the perineuronal nets described by Golgi (1893) and the perineuronal nets revealed by these lectins and antibodies. The functional role of perineuronal nets of extracellular matrix remains largely unknown (see Celio and Blümcke 1994). As a prelude to developmental and experimental stud- ies on this topic, we have produced a detailed map of the rat neurons surrounded by a Mab 1B5-immunoreactive (ir) coat containing chondroitin unsulfated proteoglycan. Previous reports concerning Mab 1B5-ir perineuronal nets in the rat focused on only a few areas of the CNS (Fujita et al. 1989; Bertolotto et al. 1991), but the distri- bution in the whole CNS has not been described. Mab 1B5 identifies the neuronal coat in both the rat, a suit- able species for experimental researches, and the human Correspondence to: R. Guglielmone&/fn-block: Cell Tissue Res (1996) 283:283–295 © Springer-Verlag 1996