Mouse P2XR7 variants, 451L and -P, are activated by ATP and histones. (A) Average ATP-evoked current as a function of ATP concentration from cells expressing mouse P2XR7 451P and 451L variants (Ave ± SEM, n = 4–7 animals, 13–21 cells). (B) Average ATP-evoked (500 μM) currents for 451P and 451L variants (Ave ± SEM, n = 4–7 animals, 20–21 cells, P = 0.0482). (C) Average histone-evoked (20 μg/ml) currents for 451P and 451L variants (Ave ± SEM, n = 4–7 animals, 20–21 cells, P = 0.2709).