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. 1998 May 1;508(Pt 3):703–720. doi: 10.1111/j.1469-7793.1998.703bp.x

Figure 5. G proteins did not mediate current activation by extracellular ATP nor the priming effect of ATP.

Figure 5

A, the priming effect of extracellular ATP was not prevented by including GDP-β-S (200 μM) in the pipette solutions in place of GTP (200 μM). Continuous whole-cell current trace recorded at a holding potential of −40 mV. The cell was exposed to ATP (200 μM) at the times indicated by the bars. Half-maximal current activation was 107 s during the first exposure to ATP and 14 s during the second exposure to ATP. The current deactivated by 50 % within 3.5 and 3 s upon removal of the first and second applications of ATP, respectively. Digitized at 100 Hz, filtered at 50 Hz. Cell capacitance, 14 pF; series resistance, 6 MΩ. B, the current activated by extracellular ATP was not irreversibly activated by including GTP-γ-S (200 μM) in the pipette solution in place of GTP. Run-down of the current activated by ATP was also not prevented by GTP-γ-S. Continuous current trace, recorded at a holding potential of −40 mV. Extracellular ATP (300 μM) was applied twice, indicated by the bars. The break in the current trace represents 10 min during which the cell was not exposed to ATP. The first (priming) application of ATP is not shown. Digitized at 100 Hz, filtered at 50 Hz. Cell capacitance, 12 pF; series resistance, 9 MΩ.