Hippocampal neurogenesis in adult Old World primates

The production of new hippocampal neurons in adulthood has been well docume nted in rodents. Recent studies have extended these findings to other mamma lian species, such as tree shrews and marmoset monkeys. However, hippocampa l neurogenesis has not been demonstrated in adult Old World primates. To in vestigate this possibility, we injected 11 adult Old World monkeys of diffe rent ages (5-23 years) with the thymidine analog bromodeoxyuridine and exam ined the fate of the labeled cells at different survival times by using neu ronal and glial markers, In the young-adult and middle-aged monkeys, we fou nd a substantial number of cells that incorporated bromodeoxyuridine and ex hibited morphological and biochemical characteristics of immature and matur e neurons. New cells located in the dentate gyrus expressed a marker of imm ature granule neurons, Turned On After Division 64 kDa protein, as well as markers of mature granule neurons including neuron specific enolase, neuron al nuclei, and the calcium-binding protein calbindin, Fewer new cells expre ssed the astroglial marker glial fibrillary acidic protein. Evidence of neu rogenesis was observed in the oldest monkeys (23 years) as well, but it app eared to be less robust. These results indicate that the adult brains of Ol d World monkeys produce new hippocampal neurons, Adult macaque monkeys may provide a useful primate model for studying the functional significance of adult neurogenesis.