The purpose of this study is to find out whether short term treatment with a antihypertensive medication prazosin, can influence the levels of a dopamine in the brain. We will examine the levels of dopamine in the the brain using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). We hypothesize that there will be no significant changes in dopamine levels in healthy individuals taking prazosin.

The purpose of this study is to find out whether short term treatment with a antihypertensive medication prazosin, can influence the levels of dopamine in the brain. We will examine the levels of dopamine in the the brain using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). The study will involve three PET scans and one MRI. One PET scan will be performed before the participants take prazosin for approximately three weeks, and the last two PET scans will be performed after the prazosin medication phase. We hypothesize that there will be no significant changes in dopamine levels in healthy individuals taking prazosin.

Inclusion Criteria:

• Healthy males and females of any ethnic origin between 19 and 45 years old

Exclusion Criteria:

• Use of any illicit drugs in past 3 months prior to randomization and/or have a current or past diagnosis of drug abuse/dependence (including alcohol)
• Current or past DSM-IV diagnosis of any Axis I psychiatric disorder
• Major psychiatric illness and/or substance dependence in first order relatives
• Current active or past suicidal ideation
• Baseline systolic blood pressure outside the normal range
• Current use of medications that could interact with prazosin (e.g. beta blockers, phosphodiesterasetype 5 inhibitors, indomethacin, verapamil, modafinil, clonidine)
• Current use or use during the previous month of medication that may affect the CNS at the time of scanning (e.g. neuroleptics, bupropion)
• Any significant abnormalities in baseline blood results (e.g. CBC, renal and hepatic indicators) or ECG readings that would preclude the use of prazosin
• Pregnancy, trying to become pregnant or breastfeeding
• Presence of metal objects in the body (e.g. some artificial joints, bone pins, surgical clips, skull plate, certain part of dental braces) or implanted electronic devices (e.g. cardiac pacemaker, neurostimulator), that preclude safe MR scanning
• Claustrophobia
• Participation in any nuclear medicine procedures that, including the dose received during participation in this study, will bring the total radiation dose over the currently approved guideline of 20mSv in a 12-month period
• Cardiovascular or cerebrovascular diseases
• History of or current neurological illnesses including seizure disorders, migraine, multiple sclerosis, movement disorders, head trauma, CVA or CNS tumor
• Abnormal body mass (defined as not within 20% of normal BMI
• Learning disability, amnesia or other conditions that impede memory and attention