AMPAR signaling mediates platelet activation. (A) AMPA dose dependently increases agonist-induced platelet activation. Platelets were incubated with AMPA and activated with TRAP. Platelet activation was measured by FACS analysis for surface PAC-1 antibody binding. n = 5 ± the SD. *, P < 0.05 versus 0 mM. (B) AMPAR antagonist inhibits AMPA-mediated increase in platelet activation. Platelets were incubated with control, CNQX, AMPA, or AMPA after CNQX, and then activated with TRAP. n = 3 ± the SD. *, P < 0.05. (C) AMPAR antagonist decreases platelet activation. Platelets were incubated with control or CNQX, and then activated or not with TRAP. n = 5 ± the SD. *, P < 0.05. (D) GluR1^−/− platelets do not respond to AMPA. Platelets from WT and GluR1^−/− mice were incubated with control or AMPA, and activated with 0.25 U/ml thrombin (Thr). n = 3 ± SD. *, P < 0.05.