Figure 6.

NMDA-induced microglial process extension requires calcium influx and purine release from pannexin channels. A–C, Qualitative images of OGB-loaded hippocampal CA1 neurons before, during, and following a 2 min application of NMDA in normal ACSF (A, top) and in TTX containing nominally free calcium ACSF (A, bottom) with the quantitative summary in B and C. D, F, Representative image (D) and quantitative summary (F) showing that in the absence of extracellular calcium, microglial process extension to NMDA is abolished. E, Sample color-coded image of an ATP-induced chemotaxis at the beginning (00:00; red) and 30 min (00:30; green). Dashed lines indicate the location of the pipette. G, Quantitative data show similar extension velocities with or without extracellular calcium during ATP application through a pipette. H–J, Microglial process extension still occurs in the presence of P2X7 receptor antagonist BBG (10 μm; H) and connexin channel blocker CBX (50 μm; I) but not in the presence of pannexin channel blocker PB (5 mm; J). K, Quantitative summary of process extension under various conditions in H–J; ***p < 0.001. a.u., arbitrary units.