Long-term survival of postembryonically born cells in the cerebellum of gymnotiform fish, Apteronotus leptorhynchus.

The gymnotiform fish Apteronotus leptorhynchus is, like all teleosts examined thus far, distinguished by its enormous potential for the production of new neurons in the adult brain. In the cerebellum, cells are generated continuously and at high rate in discrete proliferation zones. From there, they migrate into specific target areas comprised of granule cell layers in the four cerebellar subdivisions. The long-term fate of these cells was followed through labelling with 5-bromo-2'-deoxyuridine. Employment of survival times of up to 440 days after the administration of this thymidine analogue revealed that the newborn cells survive for extremely long periods of time, spanning most of the fish's adult life, without exhibiting a decline in their number. This long-term survival, together with the permanent addition of new cells to the population of older cells, forms the basis for the continuous growth of the cerebellum during adulthood.