The main olfactory bulb is now one of the most interesting parts of the brain; firstly as an excellent model for understanding the neural mechanisms of sensory information processing, and secondly as one of the most prominent sites whose interneurons are generated continuously in the postnatal and adult periods. The neuronal organization of the main olfactory bulb is fundamentally important as the basis of ongoing and future studies. In this review we focus on four issues, some of which appear not to have been recognized previously: (1) axons of periglomerular cells, (2) the heterogeneity and peculiarity of dopamine-GABAergic juxtaglomerular cells, (3) neurons participating in the interglomerular connections, and (4) newly found transglomerular cells.
Keywords: Axon; Dendrite; Glomerulus; Interneuron; Olfactory bulb.