In the postnatal mammalian brain, neurons continue to be generated and migrate to their home stations. Often, these neuroblasts travel along pathways defined by the blood vessels or the glial cells that surround and support neurons. García-González et al. also find that serotonergic axons establish neuroblast migratory pathways. Knockout of the serotonin receptor in transit-amplifying cells and neuroblasts of mice misguided and slowed migration of the new cells. The postnatal neuroblasts travel along the serotonergic axons and depend on serotonergic signaling to sustain and guide their migration. Similar serotonergic axons also characterize neuroblast migratory pathways in fish, birds, rabbits, nonhuman primates, and humans.
