Deletion of VAMP8 partially affected α-granule decondensation whereas deletion of VAMP8 in a V2^Δ3^Δbackground largely blocked α-granule decondensation. Thin section electron microscopy of V2^Δ3^Δ (A), V8^−/− (B), and V2^Δ3^Δ8^−/− (C). Platelets stimulated with thrombin for 0, 90, and 300 seconds are shown. (D) Number of platelet profiles scored: WT: (0 seconds/0 time, n = 200), (90 seconds, n = 145), (300 seconds, n = 41); V8^−/−: (0 seconds, n = 50), (90 seconds, n = 50), (300 seconds, n = 50). (E) Number of platelet profiles scored: V2^Δ3^Δ: (0 seconds, n = 100), (90 seconds, n = 50), (300 seconds, n = 50); V2^Δ3^Δ8^−/−: (0 seconds, n = 100), (90 seconds, n = 50), (300 seconds, n = 38). Means and standard errors of the mean are presented, and graphs are color coded as indicated. P values were calculated, using Student t test, and asterisks indicating statistical significance are as follows: *P = .01 to .05; **P ≤ .01. Note: The electron density of the α-granule matrix at 0 seconds appeared similar for platelets from WT and all 3 SNARE variants.