Dopaminergic Modulation of Brain Activation Using Simultaneous PET/Pharmacological MRI

Detailed Summary

Background: Dopamine (DA) is a chemical signal in the brain linked to learning, memory, and habits. Stimulant drugs like methylphenidate can increase DA in the brain. Researchers want to measure DA with and without this drug. They want to learn how methylphenidate and brain dopamine affect body responses, mood, and thinking. Objective: To better understand the role of dopamine in the brain and the effects of methylphenidate. Eligibility: Adults ages 18-55 who have used alcohol or stimulant drugs but have no drug dependence. Design: Participants will be screened with: * Physical exam * Question about medical, psychiatric, and alcohol and drug use history * Questions to see if it s safe to have a PET/MRI scan * Blood and urine tests * Breath test for alcohol Participants will have 3 or 4 study visits. At each visit they will have: * Urine and breath tested for alcohol and drugs * A thin plastic tube (catheter) inserted in each arm by needle * A small amount of radioactive chemical injected through the catheter. * PET/MRI scan. Participants will lie still on a table that slides in and out of a metal cylinder surrounded by a strong magnetic field. Their vital signs will be monitored. They will get earmuffs for loud noises. Before the scan, participants will get the study drug or placebo through the catheter. They may also get a sugar pill (placebo). They will get a small meal and have blood drawn. * Tests of memory, attention, and thinking. Participants will wear an activity monitor on the wrist for one week.

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Interventions