Regulation of adult neurogenesis in the hippocampus by stress, acetylcholine and dopamine

Neurogenesis is well-established to occur during adulthood in two regions of the brain, the subventricular zone (SVZ) and the subgranular zone (SGZ) of the dentate gyrus in the hippocampus. Research for more than two decades has implicated a role for adult neurogenesis in several brain functions including learning and effects of antidepressants and antipsychotics. Clear understanding of the players involved in the regulation of adult neurogenesis is emerging. We review evidence for the role of stress, dopamine (DA) and acetylcholine (ACh) as regulators of neurogenesis in the SGZ. Largely, stress decreases neurogenesis, while the effects of ACh and DA depend on the type of receptors mediating their action. Increasingly, the new neurons formed in adulthood are potentially linked to crucial brain processes such as learning and memory. In brain disorders like Alzheimer and Parkinson disease, stress-induced cognitive dysfunction, depression and age-associated dementia, the necessity to restore brain functions is enormous. Activation of the resident stem cells in the adult brain to treat neuropsychiatric disorders has immense potential and understanding the mechanisms of regulation of adult neurogenesis by endogenous and exogenous factors holds the key to develop therapeutic strategies for the debilitating neurological and psychiatric disorders.