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There are few fields in neuroscience that have witnessed a faster development than the field of adult neurogenesis in the past decade. The discovery of stem cells present in the adult brain that give rise to new neurons has raised a lot of interest as it changed current concepts of brain plasticity and possible strategies for brain repair. While neurogenesis, today, has become a well-acknowledged phenomenon, many open questions remain. In this special issue, we have compiled a selection of articles that address several timely topics related to neurogenesis and discuss some of the unresolved questions concerning the functional relevance of adult neurogenesis, its regulation, and its role in the diseased brain.

Several lines of evidence implicate BDNF in the pathogenesis of stress-induced depression and the delayed efficacy of antidepressant drugs. Antidepressant-induced upregulation of BDNF signaling is thought to promote adaptive neuronal plasticity through effects on gene expression, but the effector genes downstream of BDNF has not been identified. Local infusion of BDNF into the dentate gyrus induces a long-term potentiation (BDNF-LTP) of synaptic transmission that requires upregulation of the immediate early gene Arc. Recently, we identified five genes (neuritin, Narp, TIEG1, Carp, and Arl4d) that are coupregulated with Arc during BDNF-LTP. Here, we examined the expression of these genes in the dentate gyrus, hippocampus proper, and prefrontal cortex after antidepressant treatment. We show that chronic, but not acute, fluoxetine administration leads to upregulation of these BDNF-LTP-associated genes in a brain region-specific pattern. These findings link chronic effects of antidepressant treatment to molecular mechanisms underlying BDNF-induced synaptic plasticity.