Raclopride

Background:
The chemical messenger dopamine carries signals between brain cells. It may affect addiction. Heavy use of pain medicines called opioids may decrease the amount of dopamine available to the brain. Researchers want to study if decreased dopamine decreases self-control and increases impulsiveness.
Objective:
To learn more about how opiate use disorder affects dopamine in the brain.
Eligibility:
Adults 18-80 years old who are moderate or severe opiate users
Healthy volunteers the same age
Design:
Participants will first be screened under another protocol. They will:
* Have a physical exam
* Answer questions about their medical, psychiatric, and alcohol and drug use history
* Take an MRI screening questionnaire
* Give blood and urine samples
* Have their breath tested for alcohol
Participants will have up to 3 study visits.
They will have 2-3 positron emission tomography (PET) scans. A radioactive chemical will be injected for the scans. Participants will lie on a bed that slides in and out of the donut-shaped scanner. A cap or plastic mask may be placed on the head.
Vital signs will be taken before and after the PET scans.
Participants will get capsules of placebo or the study drug. They will rate how they feel before, during and after.
Participants will have their breath and urine tested each day.
Participants will have magnetic resonance imaging (MRI) scans. They will lie on a table that slides into a cylinder in a strong magnetic field. They may do tasks on a computer screen while inside the scanner.
Participants will have tests of memory, attention, and thinking.
Participants will wear an activity monitor for one week....