Characterization of [11C]Flumazenil to Image GABA Transmission in Healthy Adult Subjects and Subjects With Alcohol Dependence

Objectives: \- By comparing the two PET scans (before and after tiagabine) done in the same day, we can understand more about how much GABA your brain makes and about the activity of your GABA receptors in the brain. Eligibility: \- Individuals 18-45 years of age who are heavy drinkers or healthy controls. Design: * Procedures to determine if you are eligible to take part in a research study are called "screening procedures". This will require you to come to the investigators office for approximately ½ day. For this research study, the screening procedures include comprehensive psychiatric and medical evaluations. Participants be asked to abstain from drugs and alcohol for the duration of the study and will be required to make trips several times a week for two weeks to provide clean urine samples. * During one of the visits prior to the PET scans, participants will have a magnetic resonance image (MRI) taken of their brain. * We will be using a technology called Positron Emission Tomography (PET), which is a method used to take pictures of the body, in this case, the brain. We will be injecting you with a radiotracer called \[11C\]flumazenil. A radiotracer is a small amount of a drug with radioactivity attached. Because the radiotracer temporarily sticks to the GABA receptors in the brain, the PET scan can then measure the activity at GABA receptors by measuring the amount of the radiotracer. You will undergo two PET scans with \[11C\]flumazenil on one day for this study. After the first PET scan, you will be given an oral dose of tiagabine (Gabitril®), which is a medication approved for the treatment of seizure disorder. Tiagabine raises levels of GABA in the brain. It is used in this study so that we can measure the changes in GABA levels. Blood samples will be drawn during the PET scans.