Serotonin Mediates Cross-Modal Reorganization of Cortical Circuits

SummaryLoss of one type of sensory input can cause improved functionality of other sensory systems. Whereas this form of plasticity, cross-modal plasticity, is well established, the molecular and cellular mechanisms underlying it are still unclear. Here, we show that visual deprivation (VD) increases extracellular serotonin in the juvenile rat barrel cortex. This increase in serotonin levels facilitates synaptic strengthening at layer 4 to layer 2/3 synapses within the barrel cortex. Upon VD, whisker experience leads to trafficking of the AMPA-type glutamate receptors (AMPARs) into these synapses through the activation of ERK and increased phosphorylation of AMPAR subunit GluR1 at the juvenile age when natural whisker experience no longer induces synaptic GluR1 delivery. VD thereby leads to sharpening of the functional whisker-barrel map at layer 2/3. Thus, sensory deprivation of one modality leads to serotonin release in remaining modalities, facilitates GluR1-dependent synaptic strengthening, and refines cortical organization.

► Visual deprivation (VD) drives AMPA receptors into synapses in the rat barrel cortex ► Seoronin mediates VD-induced facilitation of synaptic AMPA receptor delivery ► VD increases activation of ERK and increase of phosphorylation of GluR1 at Ser845 ► VD sharpens the map in the barrel cortex