A UNIQUE NEURONAL GLYCOLIPID DEFINES ROSTROCAUDAL COMPARTMENTALIZATION IN THE ACCESSORY OLFACTORY SYSTEM OF RATS

A monoclonal antibody, CC6, reacts with a complex glycolipid whose exp ression in the rat is restricted to the olfactory system. Structural a nalysis reveals that the glycolipid contains two alpha-fucose branches ; one each at internal and external beta-galactose residues. Immunocyt ochemistry demonstrates in rat embryos that CC6 glycolipid expression is restricted to a subset of neurons in the vomeronasal organ (VNO) an d their corresponding axon projections in the caudal accessory olfacto ry bulb (AOB). This pattern of expression in the accessory olfactory s ystem is the converse of the pattern revealed by a previously characte rized antiglycolipid antibody that reacts with VNO neurons projecting to the rostral AOB. The CC6-reactive glycolipid is also expressed on a subset of neurons in the main olfactory epithelium. Postnatally, axon s from these CC6 positive sensory neurons converge to form a limited n umber of axon bundles running longitudinally through the nerve layer o f the main olfactory bulb. These data provide further evidence that gr oups of vomeronasal and olfactory neurons expressing unique surface mo lecules project axons that terminate in selected targets in the AOB an d OB, respectively.