NO-dependent vasodilation by corticosteroids. (a) Wall tension to cumulative concentrations of phenylephrine in aortic rings incubated with 1 μM dexamethasone (n ≥ 6). (b) Dose-dependent effects of dexamethasone on wall tension in aortic rings pretreated with 1 μM phenylephrine (n ≥ 4). (c) Wall tension in aortic rings from wild-type or eNOS–/– mice treated with phenylephrine and dexamethasone or ACh (3μM) with or without RU486, LY294002, or L-NAME (n ≥ 4). (d) Aortic eNOS activity from wild-type or eNOS–/– mice treated with vehicle or dexamethasone with or without RU486 or LY294002 for 2 hours. Three separate experiments yielded similar results. *P < 0.05.