Neurogenesis in the adult brain is now a well-recognized phenomenon. The compelling subject of interest now is that besides the intrinsic, what are the environmental factors which affect neural stem cells ability to maintain themselves and enter the pool of the adult brain. While the molecular and cellular mechanisms that regulate this process remain to be elucidated, substantial data implicate common pathways involving action of neurotransmitters through neurotrophic factors to regulate the neural stem cells. This transmitter-mediated neurotrophic factor pathway could be altered by extrinsic environmental factors including enriched environment, exercise, stress, and drug abuse (i.e. alcohol, opioid, methamphetamine). Our special attention focuses on the role of neurotransmitters; among them are serotonin (5-HT), glutamate and gamma-amino-butyric acid (GABA). Substances of abuse including alcohol, which may interact through these neurotransmitters and neurotrophic factors to affect neurogenesis, are also reviewed.
