HAG abolishes P2Y₁₂-dependent signaling but only partially inhibits CalDAG GEFI-dependent signaling in mouse platelets. Washed mouse platelets lacking CalDAG GEFI (A) or P2Y₁₂ (B) were pretreated with 10 μM HAG or DMSO for 30 minutes at room temperature and stimulated with 1.25 μg/mL convulxin. Aggregation was observed for 3 minutes (panel A, **P < .007 for HAG vs DMSO; panel B, *P < .05 for HAG vs DMSO, n = 4 for each group).