Fig. 3

The transient ATP-induced potentiation of whole-cell currents in human microglia depends on the [Ca²⁺]_i increase. a Typical I-V relation obtained by applying a single voltage ramp (from −120 mV to +40 mV, 200 ms) before and after the administration of ATP (100 μM, 10 s), on an representative human microglial cell (patient #3) out of the 11 cells recorded in the same conditions. Whole-cell currents were recorded in the voltage-clamp configuration using the perforated patch technique, to avoid cell dialysis. Please note the strong increase in the outward current after ATP. b Time course of the mean current amplitude measured at −20 mV in control conditions, averaged from 11 cells (6 from #3 and 5 from #9). Voltage ramps were applied every 2 s. Current amplitudes were normalized to the value averaged from the 5 currents preceding ATP administration. c Typical I-V relation obtained by applying a single voltage ramp before and after the administration of ATP, on a representative cell (#7) out of the 6 cells recorded in the same conditions. d Time course of the mean current amplitude measured at −20 mV in the absence of external Ca²⁺ in cells preincubated with the Ca²⁺ chelator BAPTA-AM (20 μM), averaged from 6 cells (#7). Please note that ATP-induced current potentiation is abolished if [Ca²⁺]_i increase is prevented. e Time course of the mean current amplitude measured at −20 mV in the absence of external Ca²⁺, averaged from 9 cells (#10). f Time course of the mean current amplitude measured at −20 mV in cells preincubated with the Ca²⁺ chelator BAPTA-AM (20 μM), averaged from 5 cells (#4). g Histogram representing the mean current density measured at −20 mV immediately before (gray) and after (white) the ATP administration, in different experimental conditions, as indicated. Please note that in the absence of extracellular Ca²⁺ cells preincubated with BAPTA-AM shows a reduction of basal current density along with the complete lack of ATP-induced current potentiation. The numbers of recorded cells for control (left bars), Ca²⁺-free, only BAPTA, and Ca²⁺-free + BAPTA experiments (right bars) were 13 (6 from #3, 5 from #9 and 2 from #12), 9 (#10), 5 (#4), and 6 (#7), respectively. Two asterisks denote significantly higher than before ATP, p<0.001. *p=0.025. a Mean basal value in control condition is significantly higher than in BAPTA (p=0.033) and in Ca²⁺-free + BAPTA (p=0.007). b Mean peak value in control condition is significantly higher than in Ca²⁺-free (p=0.020), in BAPTA (p=0.025), and in Ca²⁺-free + BAPTA (p=0.006)