Adult-generated hippocampal and neocortical neurons in macaques have a transient existence

Previously we reported that new neurons are added to the hippocarnpus and n eocortex of adult macaque monkeys. Here we compare the production and survi val of adult-generated neurons and glia in the dentate gyrus, prefrontal co rtex, and inferior temporal cortex. Twelve adult macaques were injected wit h the thymidine analogue BrdUrd, and the phenotypes of labeled cells were e xamined after 2 h, 24 h, 2 wk, 5 wk, 9 wk, and 12 wk by using the following immunocytochemical markers: for immature and mature neurons, class III P-t ubulin (TuJ1); for mature neurons, neuronal nuclei; for astrocytes, glial f ibrillary acidic protein; and for oligodendrocytes, 2 ' ,3 ' -cyclic nucleo tide 3 ' phosphodiesterase. We found that the dentate gyrus had many more B rdUrd-labeled cells than either neocortical area. Furthermore, a greater pe rcentage of BrdUrd-labeled cells expressed a neuronal marker in the dentate gyrus than in either neocortical area. The number of new cells in all thre e areas declined by 9 wk after BrdUrd labeling, suggesting that some of the new cells have a transient existence. BrdUrd-labeled cells also were found in the subventricular zone and in the white matter between the lateral ven tricle and neocortex; some of the latter cells were double-labeled for BrdU rd and TuJ1. Adult neocortical neurogenesis is not restricted to primates. Five adult rats were injected with BrdUrd, and after a 3-wk survival time, there were cells double-labeled for BrdUrd and either TuJ1 or neuronal nucl ei in the anterior neocortex as well as the dentate gyrus.