Depletion of VAMP2, VAMP3, and VAMP8 in platelets affects ATP/ADP release but not aggregation. Aggregation (A-C) and ATP/ADP release (D-F) were monitored simultaneously in a lumi-aggregometer. Washed platelets (4 × 10⁸/mL) from WT (black traces), V2^Δ3^Δ (dark gray traces), and V2^Δ3^Δ8^−/− (light gray traces) platelets were stimulated with 0.05 U/mL (A), 0.1 U/mL (B), or 0.5 U/mL (C) thrombin (Thr), and ATP release and aggregation were measured for 5 minutes.