In the following we will discuss the relevance that neurogenesis may play in the aetiology and/or maintenance of two selected diseases, major depression and epilepsy (for an extended review please refer to [62,63]). One of the hallmarks in the aetiology of affective disorders such as major depression is stress, which is among the most powerful negative regulators of hippocampal neurogenesis. Together with the findings that a number of clinically used antidepressants (ADs) such as fluoxetine strongly enhance neurogenesis, the idea was proposed that new neurones may be critically involved

in the disease process of depression and/or represent a potential treatment target [64–66]. This was supported by the clinical observation that a number of ADs require chronic treatment to become effective which may be due to the need for ABT-199 chemical structure AD-induced neurogenesis, which would take several weeks before drug-induced neurones become functionally integrated. An important milestone supporting the relevance of neurogenesis in major depression was a study showing that irradiation-mediated Y-27632 cost inhibition of neurogenesis substantially reduced the ability

of fluoxetine (and other ADs) to affect mood-related behaviour in rodents [67]. However, it became also evident over the last years that not all drugs with AD efficacy require proper neurogenesis to be effective (at least in rodent models of major depression) [68]. Similarly, genetically enhanced neurogenesis by itself does not have mood-manipulating effects under physiological conditions even though Inositol monophosphatase 1 this genetic, neurogenesis-enhancing approach still needs to be tested in disease models [59]. Mechanistically, the role of new neurones in the context of affective disorders may be twofold. One obvious role of neurones in the context of depressive disease lies in their function in cognitive processes that may amplify/induce disease symptoms. In addition, recent data suggest that new neurones may also directly

serve as a buffer for stress response by having a substantial impact on the hypothalamic–pituitary–adrenal (HPA) axis [69]. Even though it is clear that altered or failing hippocampal neurogenesis is certainly not the only cause of affective disorders, current efforts aim to develop novel strategies to pharmacologically enhance neurogenesis that may help treat depression or ameliorate disease symptoms [66]. In contrast to affective disorders, the key alteration in hippocampal neurogenesis after epileptic seizures is not manifested by a reduction in newborn neurone numbers but rather by an initial increase in newborn neurone numbers followed by aberrant maturation and ectopic migration within the dentate circuitry [70–74].