Specific staining of nonpyramidal cell populations of the cerebral cortex by lectin cytochemistry on semithin sections

The pattern of lectin labeling in the cerebral cortex of the cat was studie d using semithin sections. The labeling produced by some lectins (Concanava lin A, Lens culinaris, Phaseolus vulgaris-l, Phaseolus vulgaris-E, Pisum sa tivum, wheat germ agglutinin, and succynilated-wheat germ) appeared inside every neuron as small cytoplasmic granules, probably corresponding to ciste rns of endoplasmic reticulum and/or the Goigi complex. Lectins with affinit y for alpha-mannosyl residues (Pisum sativum, Lens culinaris, and Concanava lin A) stained the cell surface of a subset of cortical neurons. The labele d cells were round or polygonal, medium to large neurons present in layers Il-VI, exhibiting the morphological features of nonpyramidal cells. Previou s lectin studies of perineuronal nets have shown that these extracellular s pecializations contain N-acetylgalactosamine and N-acetylglucosamine. Our r esults show that mannose is also a component of perineuronal nets and that lectins specific for cy-mannose can be used as tools for the cytochemical d etection of a separate class of cortical neurons, which have not yet been f ully characterized. In addition, some lectins (Bandeiraea simplicifolia, Co ncanavalin A, Lens culinaris, Phaseolus vulgaris-L, Phaseolus vulgaris-E, P isum sativum, and succynilated-wheat germ agglutinin) specifically labeled a population of a type of microglia-related cells known as perivascular cel ls. The data presented here report for the first time the selective stainin g of perivascular cells and further support the hypothesis that they are di fferent from typical microglial cells. (C) 1999 Elsevier Science Inc.