Clinical Research Directory

Inclusion Criteria: * Healthy Men or women aged 60-90 Exclusion Criteria: * History of stroke * Ineligibility for MRI (e.g. soft tissue metallic implants, clips, cardiac pacemaker, cardiac defibrillator, internal pacing wires, metallic fragments, shrapnel, etc.) * Current use of more than one of the following classes of medications: beta blockers, ace inhibitors, angiotensin receptor blockers, calcium channel blockers, or diuretics * Use of any alpha blockers (terazosin, doxazosin, alfuzosin, prazosin, or tamsulosin) in the past year. * Current use of the over-the-counter supplement yohimbe * Orthostatic hypotension defined as symptomatic decrease in BP \> 20mmHg systolic or \> 10mmHg diastolic and HR increase \< 20bpm on supine to sitting or standing. * Alcohol and drug abuse * Clinically significant traumatic brain injury * History of Type I diabetes * Uncontrolled Type II diabetes * Other known medical or psychiatric comorbidity that in the investigator's opinion would compromise participation in the study or increase fall risk * Use of investigational drugs within 30 days before screening * History of hemodynamic instability * For females: pregnancy or breastfeeding