NCT06629077 · University of Wisconsin, Madison
Brain Blood Vessel Responses to Changes in Blood Flow
What this study is about
Brain blood flow will be measured during a simulated postural change test and while breathing increased levels of carbon dioxide using magnetic resonance imaging.
View original scientific description
Brain blood flow will be measured during a simulated postural change test and while breathing increased levels of carbon dioxide using magnetic resonance imaging.
Interventions
DEVICE
MRI
Participants will undergo an MRI scan while performing breathing and a simulated postural change task.
DRUG
Prazosin
A dose of prazosin will be administered based on body weight.
DRUG
Placebo
Oral placebo
Primary outcome measures
Change in blood flow
Time frame: Two study visits, up to 240 minutes
The change in intracranial blood flow during breathing and simulated postural change tasks will be measured with MRI
Change in blood velocity
Time frame: Two study visits, up to 240 minutes
The change in blood velocity during breathing and simulated postural change tasks will be measured with MRI.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Between the ages of 55-69 years
- Have a BMI less than or equal to 34.5 kg/m2
- are less than 72 in (182.88 cm) height
- Females must be postmenopausal
Exclusion criteria
- Diagnosis of Mild Cognitive Impairment (MCI) or Alzheimer's disease (AD)
- History or evidence of hepatic disease, hematological disease, or peripheral vascular disease; severe kidney injury requiring hemodialysis
- History of cardiovascular disease including: severe congestive heart failure, coronary artery disease, ischemic heart disease (stents, coronary artery bypass grafts) and tachycardia
- Uncontrolled hypertension
- History of clinically significant ischemic or hemorrhagic stroke, or significant cerebrovascular disease
- Severe untreated obstructive sleep apnea
- History of diabetes with HbA1c greater than 9.5%
- Major neurologic disorders other than dementia (e.g., MS, ALS, brain surgery, etc.)
- Current or recent (\<1 year) major psychiatric condition (Axis I) or addictive disorders
- Significant surgical history
- Other significant medical conditions at investigators' discretion
- Contraindications to MRI
- Prescribed medications that interfere with prazosin
- Lactose allergy
- lower body will not fit in lower body negative pressure (LBNP) chamber (regardless of overall height and BMI).
Where
- Madison, Wisconsin
Collaborators
National Institute of Neurological Disorders and Stroke (NINDS)
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Mar 2, 2026 · Source of record for eligibility and locations