Adult hippocampal neurogenesis: an actor in the antidepressant-like action.

Depression and anxiety are psychiatric illnesses that are major burdens in society and affect as much as 7% of the world's population. The heterogeneous nature of depression suggests an involvement of multiple distinct brain regions including amygdala, prefrontal cortex and the hippocampus, which may be responsible for the diversity of the symptoms. Besides its critical role in learning and memory, the hippocampus is one of only two areas in mammalian brain where adult neurogenesis occurs. Of the current leading hypotheses of the pathophysiology and treatment of depression, the neurogenesis hypothesis of depression deserves particular attention because changes in neurogenesis are only seen after chronic, but not acute, antidepressant treatment. This review revisits the role of adult hippocampal neurogenesis in the pathophysiology of mood disorders, especially anxiety/depression, and also in the antidepressant-like responses, especially in stressed rodents.