Effect of GIRK channel blockers on ADP-induced PAC-1 binding. PAC-1 binding in aspirin-treated, washed human platelets on ADP stimulation was measured in the presence of various inhibitors as noted. After stimulation of platelets in the dark for 10 minutes, they were diluted with Tyrode buffer and immediately analyzed on a FACSCAN flow cytometer for increases in fluorescence that correlate with GPIIb/IIIa activation. Data were calculated as median fluorescence by multiplying the median point of the cell population with the percentage of the cell population in the marker. Each bar is the average of 3 experiments ± SEM from 3 donors. *P < .05.