Fig. 2
Human microglia express functional P2X7Rs. a Representative tracing of a whole-cell current (holding voltage = − 60 mV) activated by 5 mM ATP in a free-floating primary adult human microglia. The current displayed two distinct phases: the first (Iinitial) is the immediate effect of agonist application and the second (Ifacilitate) reflects the time-dependent facilitation. b Representative tracing of a microglial current activated by 300 μM BzATP at different holding potentials (− 100 to + 40 mV). c The current-voltage (I-V) relation obtained from the peak current amplitudes of the microglia cell shown in panel b. The reversal potential is indicated by the red symbol. d Concentration-response curves for ATP and BzATP in human microglia. Symbols represent means, and vertical lines are s.e.m. of the normalized current density from 5 to 25 cells. Sigmoidal curve is the best fit obtained with a four-parameter logistic function. e Representative inhibition and recovery after a 2-min incubation in 20 μM of the P2X7R antagonist A804598. The concentration of ATP was 5 mM. f ATP-gated (5 mM) current amplitude as fraction of control #1: the current amplitude before antagonist application. Control #2 represents the IATP measured after a 2-min incubation in control ECS solution before antagonists were applied. The fact that the amplitude of control #2 is not different from that of control #1 shows that the current is fully facilitated before application of antagonist. Current is significantly inhibited by the P2X7R antagonists A438079 (50 μM, n = 15; p < 0.0001; paired t test) and A804598 (20 μM, n = 17; p < 0.0001; paired t test). The current that remains after inhibition by A804598 is unaffected by co-application of the P2X4R antagonist BX430 (5 μM, n = 10; no significant difference between A804598 alone). All antagonists were applied 2 min before ATP application