Differential development of binding sites of two lectins in the vomeronasal axons of the rat accessory olfactory bulb.

Binding of fluorochrome-conjugated lectins, Bandeiraea simplicifolia lectin-I (BSL-I) and Vicia villosa agglutinin (VVA), to the vomeronasal axons was investigated in the accessory olfactory bulb (AOB) of developing rats at embryonic day (E) 16, 18, and 20, and postnatal day (P) 0, 3, 7, 14, and 28. Intense fluorescence for VVA was first observed at E18, and the position-specific binding pattern observed in adults was established at P0; intense fluorescence for VVA was observed in the posterior 2/3 of the vomeronasal nerve layer (VNL) and glomerular layer (GL) and weak fluorescence was present in the anterior 1/3 of these layers. Fluorescence for BSL-I was observed in the posterior half of VNL and GL at P0; the area bound with BSL-I was expanded to the anterior area and intensity of the fluorescence increased as the development proceeded. At P28, binding of BSL-I was observed in the entire VNL and GL as identical to adults. These results indicate that the binding sites of BSL-I and VVA in the vomeronasal axons at the level of rat AOB develop differentially during ontogeny, suggesting that rat VN axons consist of two subpopulations expressing different glycoconjugates.