I. Intravenous Alcohol Self-Administration (IV-ASA) in humans The first phase of this project was the characterization of free-access IV-ASA in non-dependent drinkers. During the session, subjects first undergo a directed priming phase, where they are prompted to push a button to receive standardized alcohol infusions, followed by a free-access phase, where they have open access to the same infusions. Primary measures include number of button presses, average and peak BrAC. This paradigm was previously shown to be reliable (test-retest correlations >0.6) with high internal consistency among measures (r>0.7). Since then, the sample was expanded to 146 non-dependent drinkers, and confirmed significant associations between IV-ASA measures and drinking history. Self-report measures of liking drug effects and urges following priming predicted IV-ASA, and there was a strong association between IV-ASA measures and peak feelings of drug effects, liking drug effects, intoxication and stimulation. Analysis of the early phase (first 30-min) of the IV-ASA session indicated greater sensitivity to priming effects and peak subjective effects. Subjects that had higher initial rates of IV-ASA also scored higher on measures of impulsivity, and reported lower expectancies of cognitive and physical impairment, suggesting personality traits that may underlie this alcohol-seeking behavior (Stangl et al., in review). The second phase of this project focused on developing an operant paradigm, using a progressive ratio (PR) schedule that requires subjects to press the button an increasing number of times for each successive alcohol infusion. Outcome measures include the total number of rewards earned, and average and peak BrAC. This method has shown high test-retest correlations (r>0.8) for measures. Results from a larger sample (n=72) show significant association between recent drinking history and PR IV-ASA measures, with heavier drinkers showing higher BrACs and total ethanol earned. Subjective measures of alcohol effects and urges after priming were significantly associated with IV-ASA. Exposure-response analysis support the role of the rewarding and motivating effects of alcohol driving alcohol self-administration behavior. These methods will help improve our understanding of individual differences in the rewarding properties of alcohol that drive self-administration behavior. In the past year, the Section has initiated a third phase of this project to examine the influence of stress-cues and alcohol-cues, using a guided-imagery paradigm, on IV-ASA, and the effect of drinking pattern (social vs. binge) on this response. Previous research has shown that craving, particularly in response to stress and alcohol associated cues, can potently trigger alcohol seeking behavior, and can predict relapse to excessive alcohol use in dependent drinkers. However, the relationship between stress and alcohol cues and alcohol craving and subsequent consumption in non-dependent drinkers is less clear. This study was initiated in the past year and preliminary analysis of the data collected thus far suggest that the script challenges are producing the expected stress-reactivity and craving for alcohol in binge but not social drinkers. The study will be completed in the coming months and will also include examination of neuroendocrine and autonomic response measures to characterize this paradigm. This paradigm will allow us to better understand the relationship between guided imagery stress- and alcohol-cues, alcohol craving, and alcohol self-administration. Demonstration of the translation of increased craving into increased IV-ASA is particularly important for future studies examining sources of variation on stress-induced ASA, as well as the effectiveness of pharmacological agents for the treatment of AUD. II. Human Laboratory Models in Medication Development for Alcoholism The Section is invested in developing and utilizing human laboratory models to examine the effects of pharmacological agents being developed for the treatment of alcohol use disorder (AUD). These studies can complement studies in animal models for alcoholism validated for screening of novel therapeutics to help identify treatments that are likely to succeed in clinical trials, thus facilitating future medication development for AUD. The first experimental medicine initiated by the Section was designed to examine the effect of varenicline, a (nicotinic) acetylcholine receptor partial agonist, on IV-ASA in non-treatment seeking heavy drinkers. Varenicline, a medication approved for smoking cessation, has demonstrated effectiveness in reducing alcohol consumption in a rodent model of alcohol dependence and in heavy drinking humans. This study was a randomized, placebo-controlled study in 21-60 year-old non-treatment-seeking heavy drinkers in good physical and psychiatric health. Subjects underwent a baseline IV-ASA session, after which they were randomized to 3 weeks of treatment with varenicline or placebo. Following approximately 2 weeks of treatment, subjects underwent an fMRI scan using a novel Alcohol-Food Incentive Delay task to examine the effect of varenicline on brain reward systems underlying incentive motivation for alcohol, and a facial expression task to examine the neural correlates of stress-reactivity. At the end of 3 weeks of treatment, subjects repeated the IV-ASA session to measure changes in self-administration. The sample included 22 subjects (9 smokers) in the placebo group and 24 subjects (11 smokers) in the varenicline group. Subjects were heavy drinkers with an average of 6 drinks per drinking day, and average AUDIT score of 13.5. Results from the AFID task indicate significant BOLD activation in response to alcohol cues in the striatum, amygdala and posterior insula in the placebo group; this activation was significantly attenuated in the varenicline group. The varenicline group also reported lower feelings of happiness and excitement on subjective mood scales in response to alcohol cues compared with the placebo group. Subjects with higher insula activation in response to alcohol cues showed higher IV-ASA across treatment groups. Results from the faces task indicated a significant facial expression-by-medication interaction in the left amygdala. Both groups showed equivalent activation to neutral faces, but while the placebo group showed increased activation to a fearful face, the varenicline group showed no change in activation. Amygdala activation to fearful faces correlated with AUDIT scores as well as with recent drinking history. In summary, varenicline decreased BOLD activation in striato-cortico-limbic regions associated with motivation and incentive salience of alcohol reward in heavy drinkers (Vatsalya, Gowin et al., 2015; Gowin et al., in review). These findings indicate that medication repurposing of varenicline could be targeted towards reward-drinking individuals seeking help for treatment of AUD. This study also demonstrates the utility of human laboratory paradigms and the use of fMRI-derived brain biomarkers in medications development for AUD. III. Collaborative Studies: 1) Effects of ghrelin on alcohol administration in non-treatment seeking heavy drinkers (PI: Lorenzo Leggio, NIAAA). 2) Sleep disturbance and relapse in individuals with alcohol dependence: An exploratory mixed methods study (PI: Gwenyth Wallen, NIH CC). 3) The neurophysiological effects of intravenous alcohol as potential biomarkers of ketamine's rapid antidepressant effects in major depressive disorder (PI: Carlos, Zarate, NIMH).
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