Inclusion Criteria:  18 to 45 years of age Non-obese (Body Mass Index less than 30 kg/m2) Baseline systolic blood pressure between 80-140 mmHg Baseline diastolic blood pressure <90 mmHg  Exclusion Criteria:  Participants who have cardiac, vascular, respiratory, neurological and/or metabolic illness Current or previous use of anti-hypertensive medications Any known history of renal or hepatic insufficiency/disease Pregnancy (verified by negative urine test on the experimental days) or breast-feeding Current smokers, as well as individuals who regularly smoked within the past 3 years Sulfite allergy, as this is a contraindication to intravenous phenylephrine Serious mental illness including claustrophobia History of use of recreational drugs including cocaine or amphetamines Peripheral vascular disease Subject on anticoagulant treatment Subjects with a baseline systolic blood pressure <80 mmHg