Low levels of GPVI reduce deposition of platelets on collagen under shear stress. Whole blood from the indicated mice was perfused over collagen-coated glass slides at wall shear rates at and between 400 and 1300 s^–1 for 4 minutes. (A) Percent surface coverage of GPVI-FcRγ^–/– (▪), low-GPVI (□), and wild-type (▦) platelets. The results shown are the mean ± SEM after analysis of the phase-contrast images (n = 5). Statistical significance was seen between GPVI-FcRγ^–/–, low-GPVI, and wild-type at and between 400 s^–1 and 1300 s^–1 (P < .01). (B) Representative phase-contrast images after flow. The lines seen in the upper left portions of some panels are visual artifact and do not arise due to abnormalities in the collagen-coated surface.