Endothelial dysfunction is an important predictor - and a determinant - of adverse clinical outcome. Endothelial function is impaired by coronary artery stenting, a stud from our group has shown that it can be improved by platelet inhibition using clopidogrel. However, clopidogrel unresponsiveness is a known problem, and it has been show that the endothelial effects of clopidogrel tend to wane upon prolonged treatment. Whether a more effective anti-platelet therapy is able to prevent/improve not only thrombotic events but also endothelial dysfunction, with potential positive impact on clinical outcome in patients undergoing coronary artery stenting, is an important hypothesis that needs to be further investigated. To date, evidence regarding "ancillary" (non-platelet-dependent) effects of antiaggregant drugs is very limited. For instance, while their antiplatelet effects, and their beneficial effects in patients with acute coronary syndromes, have been clearly demonstrated in multicentric trials, it remains to be shown whether these drugs also protect endothelial function. Interestingly, some authors suggest that the mortality benefit observed in the PLATO study is at least in part independent of direct antiplatelet effects. No study, to date, has tested the effects of prasugrel and/or ticagrelor on endothelial function. With the present trial, the investigators plan to test the effect of clopidogrel, prasugrel and ticagrelor on endothelial function before and up to 4 weeks after coronary artery stenting. This study will provide important pathophysiologic insight on the relationship between platelet aggregation and endothelial function, two parameters that have been shown to influence patients' prognosis.