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Figure 1 Absolute change in mean luminal diameter of the left anterior descending artery (LAD) coronary artery during intracoronary infusions. Ach^–5 and Ach^–4 indicate intracoronary acetylcholine infusions, 10^–5 and 10^–4 mol/liter, respectively. = Nitroglycerin group. = Nonnitroglycerin group. *p < 0.01 versus morning control; p < 0.01 versus afternoon control; p < 0.01 versus morning Ach^–4; p < 0.01, GTN group versus non-GTN group.