The dentate gyrus continues to produce new granule neurons well into adulthood. This has been demonstrated for many mammalian species, from rodents to primates. The proliferation of granule cell precursors can be suppressed by stressful experiences, presumably via adrenal steroids. Recent evidence suggests that serotonin can enhance the production of new neurons via activation of the 5HT1A receptor. These results present the possibility that the inhibitory effects of stress on granule cell production may be prevented by 5HT1A receptor agonists.