Olfactory bulb transplantation into the olfactory bulb of neonatal rats: an autoradiographic study.

Tritiated thymidine prelabeled presumptive olfactory bulbs (E15-E17, and E19) were homotopically transplanted in unilaterally partially or totally bulbectomized neonatal rats (P1-P5). [3H]thymidine was injected to pregnant rats at the time when the large neurons of the bulb were undergoing cellular division. After postoperative survival times from 20 days to 7 months, the animals were sacrificed and processed for histological, immunohistochemical and autoradiographic observations. The nuclear autoradiographic label allowed easy recognition of the transplanted tissue in totally bulbectomized animals after short survival and in partially bulbectomized animals after long survival. The autoradiographic label was strictly confined to the transplanted tissue and intermingling of host and donor neurons was never observed. The reliability of the autoradiographic technique in our study will enable us to mark those neurons whose axons can be demonstrated, by retrograde tracing methods, to establish connections with the host brain.