Fig. 2.

GL261 cells exposed to extracellular ATP exhibit dose-dependent intracellular calcium responses and glutamate release. a Brightfield and pseudocolored photomicrographs of GL261 cells (×200 magnification). Pseudocolored images depict intracellular calcium levels under basal conditions and approximately 30 seconds after exposure to 1 μM or 1 mM ATP. In each image, bars display the pseudocolor scale, from relatively low (cool colors) to relatively high (warm colors) levels of intracellular calcium. b Traces depict the fura-2 fluorescence ratio over the course of 2 minutes for 12 cells exposed to 1 μM ATP and 1 mM ATP (arrows). c ATP dose-response curve (n = 4 wells for each treatment). Response % values are relative to the maximum response seen relative to a saturating dose of 1 mM. Error bars represent the standard error of the mean. d) Glutamate was measured in the culture medium following a 48-hour exposure of GL261 cells to vehicle control, 200 μM ATP, and 1 mM ATP (n = 6 for each treatment). Star (*) indicates statistical significance; the 1 mM ATP treatment group shows significant increases in extracellular glutamate concentrations as compared to other treatment groups (p < 0.01)