Heterotopically transplanted embryonic olfactory bulb projection neurons form selective and appropriate axonal projections over considerable distances in adult host brains.

Embryonic olfactory primordia were transplanted into the region of the septum, the adjacent lateral ventricle (LV) and olfactory tubercle (Tu) in adult host rats. After a minimum of 7 weeks, wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) were injected into the host anterior olfactory nucleus (AO). The injection retrogradely labeled the neural cell bodies in the large neuron area (the mitral and tufted cells) of the olfactory bulb (OB) transplant. In addition, the anterogradely labeled fibers projected from the host AO to the transplant. These results indicated that the transplanted mitral and tufted neurons were able to grow axons selectively to an appropriate host terminal region (the AO) and receive fibers from the AO, even when the transplant itself was in an inappropriate host site, at a considerable distance from the host AO.