Long distance transplant-to-host axon elongation without target deafferentation.

To confirm the entire course of the long distance transplant-to-host axon elongation, the Thy-1 mouse allelic system was used for marking the olfactory bulb (OB) transplant. Axons from OB transplanted into the lateral ventricle and adjacent areas extended for a long distance, through three routes, to the frontal cortical surface, to the olfactory tubercle, the primary olfactory cortex and OB. Because of the OB graft insertion from the dorsal aspect through the neocortex, the host olfactory system remained unaffected. These results demonstrated that the transplanted OB could express its intrinsic ability of the long distance axon elongation without target deafferentation and even if the OB is inserted in the rather mature host.