FIG. 4.

Effect of chloroquine on neuronal calcium homeostasis. Drugs were added after 30 s as indicated by the arrow, and their effects on neuronal cytoplasmic calcium levels were monitored using confocal microscopy. Data are expressed as the percentages of change (± SEM) in Fluo 3-AM (F530) fluorescence after subtraction of appropriate baseline values (1% DMSO for mefloquine and Locke's buffer for chloroquine). In comparison to mefloquine (100 μM [MEF100]), chloroquine (100 μM [CHQ100]) did not alter calcium homeostasis. At concentrations (2,400 μM [CHQ2400]) equivalent to that used for mefloquine, chloroquine induced a sharp but brief increase in the cytoplasmic calcium concentration that was followed by a decline below the baseline level.