FIGURE 6.

Pharmacology of lysosomal P2X4. A-C, although pipette infusion of 1 μm ATP induced little current (A), pipette infusion of 1 μm ATP and 3 μm ivermectin induced large currents in lysosomes expressing rP2X4-GFP (B). Quantification of currents at −140 mV shows strong potentiation of lysosomal P2X4 activity by 3 μm ivermectin of application of 1 μm ATP at pH 7.4 from the luminal side (C). **: p < 0.01. D, Suramin, a generic P2 receptor blocker, did not block the large currents induced by pipette infusion of 0.1 mm ATP. E, PPADS, a nonspecific P2X receptor antagonist, did not inhibit the large currents induced by pipette infusion of 0.1 mm ATP. F, quantification of currents at −140 mV at conditions as indicated. Lysosomal P2X4 currents induced by 0.1 mm ATP in the lumen were insensitive to the two common P2 receptor antagonists. Control data are the same as that shown in Fig. 3G.