Adult-born hippocampal neurons are more numerous, faster maturing, and more involved in behavior in rats than in mice.
ABSTRACT Neurons are born throughout adulthood in the hippocampus and show enhanced plasticity compared with mature neurons. However, there are conflicting reports on whether or not young neurons contribute to performance in behavioral tasks, and there is no clear relationship between the timing of maturation of young neurons and the duration of neurogenesis reduction in studies showing behavioral deficits. We asked whether these discrepancies could reflect differences in the properties of young neurons in mice and rats. We report that young neurons in adult rats show a mature neuronal marker profile and activity-induced immediate early gene expression 1-2 weeks earlier than those in mice. They are also twice as likely to escape cell death, and are 10 times more likely to be recruited into learning circuits. This comparison holds true in two different strains of mice, both of which show high rates of neurogenesis relative to other background strains. Differences in adult neurogenesis are not limited to the hippocampus, as the density of new neocortical neurons was 5 times greater in rats than in mice. Finally, in a test of function, we find that the contribution of young neurons to fear memory is much greater in rats than in mice. These results reveal substantial differences in new neuron plasticity and function between these two commonly studied rodent species.
Article: Adult-generated hippocampal and neocortical neurons in macaques have a transient existence.[show abstract] [hide abstract]
ABSTRACT: Previously we reported that new neurons are added to the hippocampus and neocortex of adult macaque monkeys. Here we compare the production and survival of adult-generated neurons and glia in the dentate gyrus, prefrontal cortex, and inferior temporal cortex. Twelve adult macaques were injected with the thymidine analogue BrdUrd, and the phenotypes of labeled cells were examined 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 beta-tubulin (TuJ1); for mature neurons, neuronal nuclei; for astrocytes, glial fibrillary acidic protein; and for oligodendrocytes, 2',3'-cyclic nucleotide 3' phosphodiesterase. We found that the dentate gyrus had many more BrdUrd-labeled cells than either neocortical area. Furthermore, a greater percentage of BrdUrd-labeled cells expressed a neuronal marker in the dentate gyrus than in either neocortical area. The number of new cells in all three 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 ventricle and neocortex; some of the latter cells were double-labeled for BrdUrd 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 nuclei in the anterior neocortex as well as the dentate gyrus.Proceedings of the National Academy of Sciences 10/2001; 98(19):10910-7. · 9.68 Impact Factor