Secreted ADP accounts for the enhanced response of G_i2α(+/G184S) platelets to collagen but not thrombin or TxA₂. Platelet aggregation was measured in response to each of the agonists indicated in the presence of a P2Y₁₂ antagonist (Cangrelor), an ADPase (apyrase), and/or a cyclo-oxygenase inhibitor, aspirin (ASA). Representative tracings are shown. The number of times each comparison was performed and the number of mouse pairs used in each part of the figure was (A) 13 times with blood from 2 pairs of mice, (B) 13 times with 2 pairs of mice, (C) 9 times with 2 pairs of mice, (D) 12 times with 4 pairs of mice, (E) 10 times with 2 pairs of mice, (F) 9 times with 2 pairs of mice, and (G) 10 times with 2 pairs of mice.