Exposure of the early gestation ovine fetus to exogenous glucocorticoids induces alterations in postnatal cardiovascular physiology, including hypertension. To determine if autonomic function and systemic vascular reactivity are altered by in utero programming prior to the development of systemic hypertension, we examined arterial baroreflex function and in vivo hemodynamic and in vitro vascular responses to vasoactive agents in 10-14 day old newborn lambs exposed to early gestation glucocorticoids. Dexamethasone (dex, 0.28 mg/kg/day) or saline was administered to pregnant ewes by intravenous infusion over 48 hours beginning at 27 days gestation (term 145 days) and lambs were allowed to deliver (n = 6 in each group). Resting mean arterial blood pressure (MABP), (77 ± 1 vs. 74 ± 3 mmHg) and heart rate (HR), (249 ± 9 vs. 226 ± 21 bpm) were similar in dexamethasone-exposed and control animals, respectively. The arterial baroreflex curve, relating changes in HR to MABP, was significantly shifted toward higher pressure in the dex-exposed lambs although no change in the sensitivity (gain) of the response was seen. In vivo changes in blood pressure in response to bolus doses of angiotensin II (20, 50, 100 ng/kg) and phenylephrine (2, 5, 10 µg/kg) were similar in the two groups. However, dex-lambs displayed greater decreases in MABP in response to ganglionic blockade with tetraethylammonium bromide (10 mg/kg) (-30 ± 3 vs. -20 ± 3 mmHg, p<0.05) and greater increases in MABP following nitric oxide synthase blockade with L-NNA (25 mg/kg) (23 ± 3 vs. 13 ± 2 mmHg, p<0.05) compared to control lambs. By in vitro wire myography, mesenteric and femoral artery microvessel contractile responses to KCl were similar whereas responses to endothelin (in mesenteric) and norepinephrine (in femoral) were significantly attenuated in dex-lambs compared to controls. Femoral vasodilatory responses to forskolin and sodium nitroprusside were similar in the two groups (n = 4). These findings suggest that resetting of the baroreflex, accompanied by increased sympathetic activity and altered nitric oxide-mediated compensatory vasodilatory function may be important contributors to programming of hypertension.