Figure 5.
Effects of TNP-ATP, PPADS, suramin, copper, zinc, BBG, A438079, and A740003 on ATP-evoked currents in SC microglia. All compounds were applied before and during ATP application (500 μm; free [Ca2+, Mg2+]o; Vh = −60 mV). A, ATP-evoked current was poorly sensitive to TNP-ATP (10 μm), a selective antagonist of P2X1R, P2X3R, and P2X4R (p > 0.05). B, PPADS (10 μm) did not prevent ATP-evoked currents. C, PPADS (50 μm) fully blocked ATP-evoked currents. Note that ATP-evoked responses were poorly reversible 3 min after the end of the PPADS application. D, Suramin (20 μm) did not inhibit ATP-evoked responses as expected for P2X7Rs. E, Suramin (200 μm) partially blocked ATP-evoked currents. F, Copper (50 μm), known to block P2X7R activity, reversibly inhibited ATP-evoked currents. G, Zn2+ (50 μm) was poorly effective on ATP-evoked currents. H, BBG (1 μm) at this concentration was poorly effective on ATP-evoked currents. I, BBG (10 μm), known at this concentration to inhibit both P2X7R and P2X4R, irreversibly inhibited ATP-evoked currents. J, A438079 (10 μm) known at this concentration to inhibit selectively murine P2X7R fully inhibited ATP-evoked currents. K, A740003 (10 μm) also known to inhibit selectively murine P2X7R fully blocked ATP-evoked currents. L, Quantification of the inhibitory effects of the antagonists on ATP-evoked responses. Inhibitions of ATP responses were as follows: −6.8 ± 5.5% (N = 6) for 10 μm TNP-ATP, 8.7 ± 3% (N = 5) for 10 μm PPADS, 70.3 ± 4.4% (N = 6) for 50 μm PPADS, 7.2 ± 3.9% (N = 6) for 20 μm suramin, 65.7 ± 7.4% (N = 5) for 200 μm suramin, 76.8 ± 3.4% (N = 13) for 50 μm Cu2+, 5.9 ± 5.6% (N = 10) for 50 μm Zn2+, 7.2 ± 3.4% (N = 10) for 1 μm BBG, 79.3 ± 4.5% (N = 5) for 10 μm BBG, 86.8 ± 1.5% (N = 5) for 3 μm A438079, 76 ± 5% (N = 5) for 3 μm A740003, 99.8 ± 0.8% (N = 5) for 10 μm A438079, and 97.4 ± 1.6% (N = 5) for 10 μm A740003. (Statistical significance: **p < 0.01, * p < 0.05). Error bars indicate SEM.