Heterogeneous expression of glycoconjugates among individual glomeruli of the hamster main olfactory bulb

Glomeruli within the main olfactory bulb (MOB) are known as areas of synapse formation between axon terminals of olfactory neurons in the olfactory epithelium and dendrites of the first relay neurons (mitral and tufted cells) in the MOB, so that they serve as functional units in olfaction. We examined expression patterns of glycoconjugates in the glomeruli of the hamster MOB by lectin histochemistry using 21 biotinylated lectins. Thirteen lectins, WGA, s-WGA, DSL, DBA, SBA, WA, SJA, RCA-I, PNA, ECL, UEA-I, PSA and LCA, showed differential binding patterns among the glomeruli. To evaluate these differential binding patterns of lectins, we analysed staining intensity of each of the 13 lectins on the level of individual glomeruli by image analysis, and classified staining intensity into five grades (negative, 1+, 2+, 3+, 4+) on the basis of results obtained. This classification enables us to make detailed comparison among individual glomeruli. We further analysed the grade of staining intensity of each of the 13 lectins in the same glomerulus in adjacent serial sections by image analysis, and found that individual glomeruli varied in combination of grades of staining intensity and kinds of lectins. These results indicate that glycoconjugates are expressed heterogeneously in individual glomeruli, and that heterogeneous expression may contribute to the topographic organization of the primary olfactory pathway.