High-affinity uptake of serotonin into immunocytochemically identified astrocytes

Primary cultures of astrocytes from neonatal rat brain were incubated with tritiated serotonin. After fixation they were stained by immunofluorescence for the astrocyte-specific marker glial fibrillary acidic protein and processed for autoradiography. Silver grain density was increased over cells positive for glial fibrillary acidic protein and was reduced to background levels when sodium was omitted from the medium or the specific inhibitors of serotonin uptake fluoxetine and chlorimipramine were present. The results indicate that mammalian astrocytes can take up serotonin by a sodium-dependent, high-affinity system previously thought to be the exclusive property of serotonergic nerve endings.