Role of polysialic acid on outgrowth of rat olfactory receptor neurons.

Towards elucidating the role of polysialic acid (PSA) in developing olfactory neuron of the rat, we injected neuraminidase (endo-N) into the olfactory nerve pathway under whole embryo culture, then employed immunohistochemistry to (i) detect expression of highly sialylated neural cell adhesion molecules (NCAM-H) and (ii) identify olfactory neurons via anti-microtubule-associated protein 1B (MAP1B) antibody. Olfactory axonal outgrowth from basal lamina occurred at the 31-somite stage and reached the olfactory bulb primordium at the 42-somite stage, being coincident with the timing and expression of NCAM-H immunoreactivity. Enzymatic removal of PSA by endo-N remarkably affected developmental processes of axonal outgrowth, extension, and pathfinding, i.e. individual axons appeared to have become stuck in the mesenchyme. Results indicate that PSA is critically involved with anti-adhesion cues associated with individual axonal growth during olfactory system development.