Peritoneal macrophages express the serotonin transporter

Although it is known that macrophages take up serotonin, a specific monoamine transporter has not been identified in macrophages. In this study, mRNA coding for the serotonin transporter (SERT) was detected with the reverse transcription-polymerase chain reaction (RT-PCR) in recruited mouse peritoneal macrophages. Sequencing confirmed the identity of the RT-PCR product to mouse SERT mRNA. SERT protein was detected by Western blotting. Macrophage activation with lipopolysaccharide had no effect on expression of SERT mRNA or protein. Consistent with expression of a functional SERT, specific uptake of 3H-serotonin in macrophages was sodium dependent and inhibited by fluoxetine (IC50 6.9 nM) and desipramine (IC50 32 nM) but not by nisoxetine or reserpine.