Serotonin uptake by BMDCs. (A-B) [³H]5-HT uptake by BMDCs and whole mouse brain synaptosomes at 4°C (▪) and 37°C (○) and specific uptake (▵) versus 5-HT concentration. Data are from a single experiment performed in duplicate and are representative of 3 independent experiments. Note that brain protein concentration was about 5 times greater than BMDCs. The smooth curves are fits to a hyperbolic function used to derive K_m and V_max (see “Serotonin uptake by DCs”). The stated K_m values are the means (± SE) from 3 experiments with BMDCs and brain synaptosomes. (C) Mean inhibition of specific [³H]5-HT (100 nM) uptake by fluoxetine (200 nM) in BMDCs and brain. Data are means (± SD) from 2 experiments (^*P < .05, paired t test). (D) Day 5 BMDCs were purified by cell sorting for CD11c-PE-Cy7⁺ cells and then loaded with 5-HT (100 μM). LAMP-1 and 5-HT were visualized by confocal microscopy with antibodies labeled with Alexa Fluor 488 (green; i) and Alexa Fluor 546 (red; ii), respectively. Nuclei were counterstained with TO-PRO-3 (blue). In the red, green, and blue overlay (iii), the yellow signal indicates regions of red/green overlap. Scale bar represents 20 μm. (E) Magnification of bright field (i) and red/green/blue overlay (ii) from a single DC. Scale bar represents 10 μm.