Soybean agglutinin binding to the olfactory systems of the rat and mouse.

The binding of the lectin soybean agglutinin (SBA) to the olfactory system of both the rat and mouse was investigated histochemically. SBA bound to fibers in the accessory olfactory nerve and to glomeruli in the accessory olfactory bulb. In addition, SBA binding sites were present in some, but not all, glomeruli in the ventrolateral and ventromedial portions of the main olfactory bulb of only the rat. Under standard experimental conditions, SBA did not bind to neurons in other regions of the olfactory system nor to any other neurons in the brain. This selective binding of SBA to only some glomeruli in the olfactory bulb provides additional support for the presence of, at least, two subclasses of olfactory receptor cells in the nasal cavity. Whether these neuronal subclasses are the same as those previously characterized by monoclonal antibodies in rabbit remains to be determined.