<qa>  What is the name of the radioactive dopamine antagonist?We propose classification of subjects as low response or high response on the basis of their level of response to a controlled alcohol challenge in the laboratory, using the established methods of Schuckit et al to gather systematic data on subjects response to alcohol. Next, baseline levels of dopamine D2 receptor density in mesolimbic reward circuits of subjects in each group would be assessed in the PET scanner by using the radioactive dopamine antagonist C-11 raclopride. C-11 raclopride binds to D2 receptors, which will provide a signal proportional to the number of D2 receptors present. This will allow us to measure and compare the baseline D2 receptor density in high and low response groups. Directly after obtaining this baseline D2 receptor measurement, we propose administration of a controlled alcohol challenge. Acute alcohol administration causes release of dopamine in the striatum, and can dislodge a portion of the C-11 raclopride that was bound to D2 receptors. This will allow us to compare high and low response groups for differences in the displacement of C-11 raclopride induced by dopamine release, thereby providing a measure of dopamine release in response to alcohol. 