Birth Regulates the Initiation of Sensory Map Formation through Serotonin Signaling

•The birth of pups regulates initiation of barrel formation in cerebral cortex•The birth of pups leads to the reduction of 5-HT•5-HT reduction is necessary and sufficient for birth’s effect on barrel formation•Birth and 5-HT also regulate eye-specific segregation in the visual thalamus

SummaryAlthough the mechanisms underlying the spatial pattern formation of sensory maps have been extensively investigated, those triggering sensory map formation during development are largely unknown. Here we show that the birth of pups instructively and selectively regulates the initiation of barrel formation in the somatosensory cortex by reducing serotonin concentration. We found that preterm birth accelerated barrel formation, whereas it did not affect either barreloid formation or barrel structural plasticity. We also found that serotonin was selectively reduced soon after birth and that the reduction of serotonin was triggered by birth. The reduction of serotonin was necessary and sufficient for the effect of birth on barrel formation. Interestingly, the regulatory mechanisms described here were also found to regulate eye-specific segregation in the visual system, suggesting that they are utilized in various brain regions. Our results shed light on roles of birth and serotonin in sensory map formation.