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. 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 over 200 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. 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 are helping to improve our understanding of individual differences in the rewarding properties of alcohol that drive self-administration behavior. In the past year, the Section has completed 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 craving and subsequent consumption in non-dependent drinkers is less clear. In this recently completed study, social and binge drinkers underwent IV-ASA following exposure to stress, alcohol and neutral cues using guided imagery scripts. Comparison of measures of cue-reactivity, craving and IV-ASA between binge and non-binge drinkers revealed robust differences. Binge drinkers had higher craving following stress and alcohol cues compared to non-bingers (p<0.02). Binge drinkers had greater IV-ASA compared to non-binge drinkers following stress and alcohol cues (all ps <0.05). Maximum ACTH and CORT levels for stress and alcohol cues were higher in binge-drinkers (all ps<0.05) (Stangl et al., in preparation). These data provide important information on the relationship between stress and alcohol seeking behavior that may underlie risk for alcohol-related problems, and may provide an experimental paradigm to examine the effectiveness of pharmacological agents for the treatment of AUD, particularly those that target the stress system. 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 conducted by the Section examined the effect of varenicline, a (nicotinic) acetylcholine receptor partial agonist approved for smoking cessation, in non-treatment seeking heavy drinkers. 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. Participants underwent a baseline IV-ASA session, after which they were randomized to 3 weeks of treatment with varenicline or placebo. Following 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. 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 (Vatsalya, Gowin et al., 2015). 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 (Gowin et al., 2016). 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. Currently, the Section is conducting a study examining the effect of opioid receptor modulation using nalmefene on IV-ASA and neural response to alcohol cues, and the moderating role of OPRM1 gene variation on these effects, in heavy drinkers. This study could provide important information about the underlying mechanisms of opioid receptor modulation in alcohol response, and could provide novel data to enable treatment providers to develop personalized medicine approaches to increase the likelihood of therapeutic benefit of nalmefene and other opioid antagonists in the treatment of 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). 4) Ethanol response in Essential Tremor: clinical and neurophysiological correlates (PI: Mark Hallett, NINDS).
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