Efferent and afferent projections of the transplanted olfactory bulb: DiI study

This study of projections of olfactory bulb transplants to higher olfactory centres was accomplished with fluorescent carbocyanine dye DiI applied in two different ways. After a unilateral olfactory bulbectomy in neonatal rat s (3-5 days old), autoradiographically prelabelled, presumptive olfactory b ulbs from E15-17 embryos were transplanted in place of the removed tissue. Three months after surgery the anaesthetized animals were perfusion fixed a nd a crystal of carbocyanine dye DiI was inserted into the putative transpl ant. In the second part of our investigation. DiI crystals were applied dir ectly to the embryonic tissue at the time of transplantation. The appearanc e of DiI labelling differed depending on whether it was used in fixed tissu e or in vivo. Both experimental paradigms resulted in the re-establishment of connections between the transplanted olfactory bulb and olfactory relate d structures in the host brain.