The purpose of this study is to understand how the nervous system communicates to blood vessels to increase blood pressure during stress. The study will also investigate how hypertension and obesity influence the nervous system and vascular function. The study will involve measuring sympathetic nervous system activity and blood flow during common laboratory physiological stress protocols (e.g. hypoxia, exercise), and in response to infusion of drugs that cause vasodilation or vasoconstriction.

Inclusion Criteria:

• Control - BMI<30, age 18-55
• Hypertensive - BMI<30, age 18-55, diagnosis of hypertension by 24-hour ambulatory blood pressure monitoring Obese- BMI>30, age 18-55 Obese-hypertensive- BMI>30, age 18-55, diagnosis of hypertension by 24-hour ambulatory blood pressure monitoring

Exclusion Criteria:

All groups - presence of other significant cardiovascular disease, renal disease, history of smoking, diabetes,