Monoclonal antibody immunohistochemistry of a temporal relationship between axonal elimination of aberrant olfactory nerves and synaptogenesis in the rabbit olfactory bulb during middle embryonic periods.

Immunostaining using olfactory nerve- and synaptic vesicle protein-specific monoclonal antibodies revealed their characteristic appearance in the rabbit olfactory bulb during prenatal development. Prior to formation of glomeruli, olfactory nerve fibers extended beyond their target region deep into the bulb zones. Subsequently the aberrant axons decreased in number, and correspondingly, synaptic vesicle protein occurred in the innermost region of the olfactory nerve layer. It is concluded that the lack of synaptogenesis causes axonal elimination of aberrant olfactory nerves. Present results support the hypothesis that supernumerary axons degenerate unless synaptic contacts are secured; the olfactory nerves must arrive at the appropriate terminal zone in the glomeruli.