Roles for serotonin in neurodevelopment: more than just neural transmission

During pre- and early postnatal development, the neurotransmitter serotonin (5-HT) modulates cell proliferation, migration and programmed cell death, as well as cell shape and cell-cell coupling. These “trophic” effects of 5-HT, involving the cytoskeletal function, the cell cycle, and programmed cell death, can be both dependent and independent of the changes in resting membrane potential that typically define neurotransmitter action. The morphogenetic role of 5-HT is neither limited to the central nervous system (CNS), nor does it impinge upon just a single aspect of cell biology. Ontogenic differences in regional and temporal expression patterns of 5-HT receptors mediating these effects in different systems add further complexity. This review summarizes neurobiological evidence for the trophic involvement of 5-HT during development and discusses related medical issues, including potential teratological risks and possible novel therapeutic indications of selective serotonin reuptake inhibitor (SSRI) administration.