<qa>  What is the name of the radioactive substance used for PET scanning?Participants will again take a breathalyzer test for alcohol and provide a urine sample for drug screen and, for women, a pregnancy test. Subjects will lie on a hospital bed and three IV lines will be inserted, one to draw blood samples, one to infuse alcohol, and one to give raclopride, a radioactive substance used for positron emission tomography PET scanning. For PET, the subject lies on a table in the scanner with a mask placed over his or her head to help hold the head still during the scan. After a brief scan to adjust the machine, a small amount of radioactive water O-15 water is injected through the IV line and a series of pictures is taken over a period of about 1 minute. These images show how the radioactive water distributes in the brain, indicating blood flow. After the water scan, raclopride is given through the IV line and more pictures of the brain are taken over the next 2 hours. Blood samples are collected during and after the raclopride scan. During this procedure, subjects are asked the same questions about their feelings in response to the alcohol as they did during the earlier session. After he scans, they will be monitored in the clinic with hourly blood tests and questionnaires until the blood alcohol concentration decreases to 0.02 gdL and will then be sent home in a taxi. 