Researchers have identified a potential new role for the neurotransmitter serotonin that could explain a heretofore unknown evolutionary mystery.

Over the course of human evolution, the brain in particular the neocortex grew larger than our primate relatives, enabling us to think, speak and dream. The underlying mechanism of this neocortical expansion is unclear, with a number of potential molecular players having been identified. Each identified molecule is believed to act intrinsically in the basal progenitor cells of the developing neocortex, influencing its growth.

Now, researchers from the Max Planck Institute of Molecular Cell Biology and Genetics (Dresden, Germany) have identified serotonin as an additional player in this evolutionary expansion. In contrast to the previously identified molecules, serotonin is thought to act extrinsically to the progenitor cells, behaving as a growth factor in the developing brain.

Depression and anxiety: what is the scientific difference?

The biochemical differences between depression and anxiety have been elucidated, providing new insights for targeting treatment.

Placenta-derived serotonin reaches the brain via blood circulation and has been identified in both human and mice embryos, though its function in the developing brain remained a mystery. In the recent study, researchers identified the receptor HTR2A, which is found in human but not mice neocortices, leading the team to believe it may play a role in the development of the larger human brain. Indeed, when mice were genetically engineered to express the HTR2A receptor, they were found to develop much larger than normal neocortices.

We found that serotonin, by activating this receptor, caused a chain of reactions that resulted in the production of more basal progenitors in the developing brain. More basal progenitors can then increase the production of cortical neurons, which paves the way to a bigger brain, explained lead author Lei Xing.

Abnormal signaling of serotonin and a disturbed expression or mutation of its receptor HTR2A have been observed in various neurodevelopmental and psychiatric disorders, such as Down syndrome, attention deficit hyperactivity disorder and autism, commented research team leader Wieland Huttner. Our findings may help explain how malfunctions of serotonin and its receptor during fetal brain development can lead to congenital disorders and may suggest novel approaches for therapeutic avenues.

Follow this link:
Role of Serotonin in The Developing Brain - BioTechniques.com