Recent reports show that young-adult binge drinking has become a major public health problem. Nevertheless, the neurochemistry associated with this type of alcohol misuse has not been extensively studied. Previous radiotracer imaging studies in alcohol dependence have reliably shown that this disorder is associated with a reduction in dopamine type 2/3 (D2/3) receptor binding in addition to a decrease in dopamine transmission of the ventral striatum. Studies in alcohol-preferring rodents show similar results. In addition, functional MRI studies have shown that alcohol dependence is associated with a loss of reward-related activation in the ventral striatum. The goal of this study is to measure these parameters of dopamine transmission in young- adult binge drinkers compared to control subjects. Using PET radioligand imaging, we will measure both D2/3 receptor binding in addition to changes in extracellular dopamine in response to a psychostimulant challenge. We will also image, for the first time in human subjects, the kappa receptor in vivo. Previous pre-clinical studies suggest that alcohol exposure is associated with an increase in endogenous dynorphin and a downregualtion of the kappa receptor. All subjects will also undergo an fMRI using the monetary incentive delay task, a task that is associated with decreased ventral striatal activation in alcohol dependence. We will also investigate the correlation between dopamine transmission measured with PET and activation measured with fMRI in the ventral striatum in the same subjects. In addition, this application will explore the correlations between the brain measures obtained, including the correlation between pre-synaptic dopamine function measured with PET and fMRI and the association between kappa receptor availability and dopamine transmission. It has previously been hypothesized that the decrease in dopamine transmission see in alcohol dependence is associated with a "reward deficiency syndrome". A possible mechanism for this is dynorphin signaling at the kappa receptor. Thus, in this study, we have proposed a set of specific aims that are designed to measure dopamine transmission and reward-related activation with the hypothesis that disruptions in striatal dopamine transmission underlie excessive alcohol consumption in this vulnerable population.
Previous studies have shown deficiencies in the brain neurotransmitter dopamine in alcohol dependence. This decrease in dopamine transmission is thought to play an important role in disruptions in normal reward processing. The goal of the present study is to investigate whether these alterations are present in young-adult binge drinkers, and to investigate potential mechanisms behind the disruptions in dopamine transmission.