Sympathetic Regulation of Large Artery Stiffness in Humans With ISH

Inclusion Criteria: * age 60-85 * non-smoking * clinically healthy * untreated or treated stage 1 isolated systolic hypertension (ISH) (systolic BP 130-139 mmHg; diastolic BP \<90 mmHg) or stage 2 ISH (systolic BP 140-159 mmHg; diastolic BP \<90 mmHg) per 2017 AHA/ACC hypertension guidelines * if subject is on antihypertensive medications, they will stop taking medication for a one-week washout period after Visit 1 before they return for Visit 2. They will come in at day 3 and day 7 of the one-week washout for a BP reading, to confirm that systolic BP is \<160 mmHg. Exclusion Criteria: * no history of cardiovascular disease (e.g., myocardial infarction, bypass surgery, angioplasty/stent, heart failure, cardiomyopathy, pacemaker/defibrillator, peripheral artery disease), pulmonary disease, liver disease, Type I or II diabetes, cancer (treated by chemotherapy and/or radiation), psychiatric illness, on aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs). * aspirin, NSAIDs, vitamins, herbal supplements, omega-3-fatty acids will have to discontinue for at least 1 week before participation and remain discontinued during the study. * blood thinners, serotonin reuptake inhibitors (SSRIs), or PDE5 inhibitors will also be excluded. * Women must be postmenopausal for at least 6 months (surgical or natural) and not currently on hormone replacement therapy. * Subjects not on antihypertensive will not be eligible if their resting clinic systolic BP is \<130 mmHg or \>160 mmHg and diastolic BP \>90 mmHg.