Effects of YD-3 on rabbit platelet aggregation induced by thrombin (0.1 u ml−1), collagen (10 μg ml−1), platelet-activating factor (PAF, 2 ng ml−1), arachidonic acid (AA, 10 μM) and U46619 (2 μM). Washed rabbit platelets were preincubated with DMSO (0.5%, control, open columns) or YD-3 (hatched columns, 50 μM versus thrombin-induced platelet aggregation, but 100 μM versus those caused by other inducers) at 37°C for 3 min, the inducer was then added to trigger the aggregation. Percentages of inhibition are presented as mean±s.e.mean (n=5–6). ***P<0.001 as compared with the respective control.