The SK blocker, apamin, does not affect microglial phagocytosis. Phagocytosis of fluorescein-labeled E. coli bacteria was quantified using a fluorescence plate reader (see Methods), expressed as mean±SEM of the number of cell cultures indicated on each bar. To generate a phagocytosis index, data were normalized to the mean fluorescence signal from untreated microglia that had phagocytosed E. coli. Phagocytosis was not affected by a high concentration of apamin (100 nM) that blocks cloned SK1, SK2 and SK3 channels. In control experiments, phagocytosis was prevented by the actin-polymerization inhibitor, 10 μM cytochalasin D (***p < 0.001) compared with its solvent, 0.2% DMSO. The signal from DMSO treated microglia did not differ from untreated cells (p = 0.50).