To Infuse or Ingest in Human Laboratory Alcohol Research

Enhancing translation: A need to leverage complex preclinical models of addictive drugs to accelerate substance use treatment options

Preclinical models of addictive drugs have been developed for decades to model aspects of the clinical experience in substance use disorders (SUDs). These include passive exposure as well as volitional intake models across addictive drugs and have been utilized to also measure withdrawal symptomatology and potential neurobehavioral mechanisms underlying relapse to drug seeking or taking. There are a number of Food and Drug Administration (FDA)-approved medications for SUDs, however, many demonstrate low clinical efficacy as well as potential sex differences, and we also note gaps in the continuum of care for certain aspects of clinical experiences in individuals who use drugs. In this review, we provide a comprehensive update on both frequently utilized and novel behavioral models of addiction with a focus on translational value to the clinical experience and highlight the need for preclinical research to follow epidemiological trends in drug use patterns to stay abreast of clinical treatment needs. We then note areas in which models could be improved to enhance the medications development pipeline through efforts to enhance translation of preclinical models. Next, we describe neuroscience efforts that can be leveraged to identify novel biological mechanisms to enhance medications development efforts for SUDs, focusing specifically on advances in brain transcriptomics approaches that can provide comprehensive screening and identification of novel targets. Together, the confluence of this review demonstrates the need for careful selection of behavioral models and methodological parameters that better approximate the clinical experience combined with cutting edge neuroscience techniques to advance the medications development pipeline for SUDs.

The Continuing Challenges of Studying Parallel Behaviours in Humans and Animal Models

The use of animal models continues to be essential for carrying out research into clinical phenomena, including addiction. However, the complexity of the clinical condition inevitably means that even the best animal models are inadequate, and this may go some way to account for the apparent failures of discoveries from animal models, including the identification of potential novel therapies, to translate to the clinic. We argue here that it is overambitious and misguided in the first place to attempt to model complex, multifacetted human disorders such as addiction in animals, and especially in rodents, and that all too frequently "validity" of such models is limited to superficial similarities, referred to as "face validity", that reflect quite different underlying phenomena and biological processes from the clinical situation. Instead, a more profitable approach is to identify (a) well-defined intermediate human behavioural phenotypes that reflect defined, limited aspects of, or contributors to, the human clinical disorder, and (b) to develop animal models that are homologous with those discrete human behavioural phenotypes in terms of psychological processes, and underlying neurobiological mechanisms. Examples of past and continuing weaknesses and suggestions for more limited approaches that may allow better homology between the test animal and human condition are made.

Sex differences in alcohol's effects on fronto-amygdalar functional connectivity during processing of emotional stimuli

BACKGROUND

Amygdala function underlying emotion processing has been shown to vary with an individuals' biological sex. Expanding upon functional magnetic resonance imaging (fMRI) findings reported previously where a low level of response was the focus, we examined alcohol and sex effects on functional connectivity between the amygdala and other brain regions. The central hypothesis predicted that sex would influence alcohol's effects on frontal-limbic functional circuits underlying the processing of negative and positive facial emotions.

METHODS

Secondary analyses were conducted on data from a double-blind, placebo controlled, within-subjects, cross-over study in 54 sex-matched pairs (N = 108) of 18- to 25-year-old individuals without an alcohol use disorder at baseline. Participants performed an emotional faces fMRI processing task after placebo or approximately 0.7 mL/kg of ethanol. Psychophysiological interaction analyses examined functional connectivity between the amygdala with other brain regions.

RESULTS

There were significant alcohol-by-sex interactions when processing negatively valenced faces. Whereas intoxicated men exhibited decreased functional connectivity between the amygdala and ventral and dorsal anterior cingulate, angular gyrus, and middle frontal gyrus connectivity was increased in intoxicated women. There was also a main sex effect where women exhibited less functional connectivity in the middle insula than men regardless of whether they received alcohol or placebo. For happy faces, main effects of both sex and alcohol were observed. Women exhibited less amygdala functional connectivity in the right inferior frontal gyrus than men. Both men and women exhibited greater functional connectivity in the superior frontal gyrus in response to alcohol than placebo.

CONCLUSIONS

Alcohol's effects on amygdala functional circuits that underlying emotional processing vary by sex. Women had higher functional connectivity than men following exposure to a moderate dose of alcohol which could indicate that women are better than men at processing affectively laden stimuli when intoxicated.

A randomized trial of the effects of COMT inhibition on subjective response to alcohol: Moderation by baseline COMT activity and mediation of alcohol self-administration

BACKGROUND

Poor inhibitory control and enhanced subjective response to alcohol are interrelated risk factors for alcohol use disorder (AUD) that share underlying neural substrates, including dopamine signaling in the right prefrontal cortex, a potential target for pharmacological intervention. Cortical dopamine inactivation is primarily regulated by catechol-O-methyltransferase (COMT), an enzyme with large variation in activity as a function of the COMT rs4680 (val158met) single nucleotide polymorphism. In a previous randomized, placebo-controlled trial of the COMT inhibitor tolcapone (200 mg TID) in non-treatment-seeking participants with AUD, we found that tolcapone, relative to placebo, reduced alcohol self-administration only among rs4680 val-allele homozygotes, whose COMT activity is higher than in met-allele carriers.

METHODS

We conducted secondary analyses of the effects of tolcapone and baseline COMT activity, as indexed by both rs4680 genotype and an enzymatic activity assay, on the subjective response to alcohol in a bar-laboratory paradigm among 60 participants in the previous trial.

RESULTS

Tolcapone did not affect alcohol-induced stimulation or sedation more than placebo. However, baseline COMT activity moderated the effects of the drug on both outcomes, such that tolcapone-treated participants with higher baseline COMT activity had less stimulation (p = 0.008) and sedation (p = 0.053) than participants with lower baseline COMT activity and those treated with placebo. Additionally, alcohol-induced stimulation significantly mediated the interacting effects of baseline COMT activity and tolcapone on bar-laboratory self-administration.

CONCLUSIONS

Tolcapone may reduce subjective response to alcohol more effectively among individuals with preexisting high COMT activity an effect that could account for the drug's reduction of alcohol consumption among these individuals.

High-intensity sweet taste as a predictor of subjective alcohol responses to the ascending limb of an intravenous alcohol prime: an fMRI study

High-intensity sweet-liking has been linked to alcohol use disorder (AUD) risk. However, the neural underpinning of this association is poorly understood. To find a biomarker predictive of AUD, 140 participants (social and heavy drinkers, ages 21-26) underwent functional magnetic resonance imaging (fMRI) during a monetary incentive delay (MID) task and stimulation with high (SucroseHigh)- and low-concentration sucrose, as well as viscosity-matched water. On another day after imaging, and just before free-access intravenous alcohol self-administration, participants experienced a 30 mg% alcohol prime (10 min ascent) using the Computerized Alcohol Infusion System. Principal component analysis (PCA) of subjective responses (SR) to the prime's ascending limb generated enjoyable (SRenjoy) and sedative (SRsed) intoxication components. Another PCA created one component reflective of self-administered alcohol exposure (AE) over 90 min. Component loadings were entered as regressors in a voxel-wise general linear fMRI model, with reward type as a fixed factor. By design, peak prime breath alcohol concentration was similar across participants (29 ± 3.4 mg%). SRenjoy on the prime's ascending limb correlated positively with [SucroseHigh > Water] in the supplementary motor area and right dorsal anterior insula, implicating the salience network. Neither SR component correlated with the brain's response to MID. AE was unrelated to brain reward activation. While these findings do not support a relationship between alcohol self-administration and (1) subjective liking of or (2) regional brain response to an intensely sweet taste, they show that alcohol's enjoyable intoxicating effects on the rising limb correspond with anterior insular and supplementary motor area responses to high-concentration sucrose taste. No such associations were observed with MID despite robust activation in those regions. Insula and supplementary motor area responses to intense sensations relate to a known risk factor for AUD in a way that is not apparent with a secondary (monetary) reward.

Association Between Fatty Acid Amide Hydrolase and Alcohol Response Phenotypes: A Positron Emission Tomography Imaging Study With [11C]CURB in Heavy-Drinking Youth

BACKGROUND

Reductions in fatty acid amide hydrolase (FAAH), the catabolic enzyme for the endocannabinoid anandamide, may play a role in drinking behavior and risk for alcohol use disorder. We tested the hypotheses that lower brain FAAH levels in heavy-drinking youth are related to increased alcohol intake, hazardous drinking, and differential response to alcohol.

METHODS

FAAH levels in the striatum, prefrontal cortex, and whole brain were determined using positron emission tomography imaging of [11C]CURB in heavy-drinking youth (N = 31; 19-25 years of age). C385A FAAH genotype (rs324420) was determined. Behavioral (n = 29) and cardiovascular (n = 22) responses to alcohol were measured during a controlled intravenous alcohol infusion.

RESULTS

Lower [11C]CURB binding was not significantly related to frequency of use but was positively associated with hazardous drinking and reduced sensitivity to the negative effects of alcohol. During alcohol infusion, lower [11C]CURB binding related to greater self-reported stimulation and urges and lower sedation (p < .05). Lower heart rate variability was related to both greater alcohol-induced stimulation and lower [11C]CURB binding (p < .05). Family history of alcohol use disorder (n = 14) did not relate to [11C]CURB binding.

CONCLUSIONS

In line with preclinical studies, lower FAAH in the brain was related to a dampened response to the negative, impairing effects of alcohol, increased drinking urges, and alcohol-induced arousal. Lower FAAH might alter positive or negative effects of alcohol and increase urges to drink, thereby contributing to the addiction process. Determining whether FAAH influences motivation to drink through increased positive/arousing effects of alcohol or greater tolerance should be investigated.

Stimulant-like subjective effects of alcohol are not related to resting-state connectivity in healthy men

Individual differences in subjective, stimulant-like effects of alcohol are associated with the risk of developing alcohol use disorder. Specifically, individuals who experience more pronounced stimulant-like effects from alcohol are more likely to continue and escalate their usage. The neural basis for these individual differences in subjective response is not yet known. Using a within-subject design, 27 healthy male social drinkers completed three fMRI scans after ingesting a placebo, 0.4 and 0.8 g/kg alcohol, in a randomized order under double-blind conditions. Subjective stimulant effects of alcohol were assessed at regular intervals during each session. Seed-based and regional homogeneity analyses were conducted to evaluate changes in resting-state functional connectivity in relation to the stimulant effect of alcohol. Results indicated that 0.4 g/kg alcohol increased the connectivity to thalamus, and 0.8 g/kg alcohol decreased the connectivity to ventral anterior insula, primarily from the superior parietal lobule. Both doses reduced regional homogeneity in the superior parietal lobule but without an exact overlap with clusters showing connectivity changes in the seed-based analyses. The self-reported stimulant effect of alcohol was not significantly related to changes in seed-based connectivity or regional homogeneity. These findings suggest that alcohol-induced stimulation effects are not related to these indices of neural activity.

Subjective response to alcohol: Interactive effects of early life stress, parental risk for mood and substance use disorders, and drinking context

Early life stress, specifically childhood maltreatment, and parental risk for mood and substance use disorders (SUDs) are associated with increased risk for alcohol use disorder (AUD). There is limited data on how these factors interact to contribute to alcohol-related outcomes. Prior work has suggested early life stress may increase sensitivity to psychostimulants and that subjective response to alcohol is heritable. It is unclear if early life stress alters sensitivity to alcohol and interacts with parental risk for mood/SUDs, which in turn may act as a risk factor for AUD. The current study uses within-subjects placebo-controlled alcohol administration methods to investigate the effects of childhood maltreatment on subjective response to alcohol in young adults with and without parental risk of mood/SUDs. Additionally, we explored interactions with drinking context (i.e., drinking in a bar vs. non-bar context). Within individuals with parental risk for mood/SUDs, there was a positive relation between total Childhood Trauma Questionnaire (CTQ) score and how drunk individuals reported feeling across both alcohol and placebo conditions (parental risk group-by-CTQ interaction p = .01; main effect of CTQ within individuals with parental risk for mood/SUDs p = .005). When exploring interactions with drinking context (bar vs. non-bar context), we observed a significant drinking context-by-parental risk-by-CTQ interaction (p = .03), with CTQ score positively associated with greater positive valence/positive arousal feelings in the parental risk group if they consumed their beverages in the bar context (p = .004) but not if they consumed their beverages in the non-bar context. Results suggest childhood maltreatment may contribute to variation in subjective response to the positive effects of alcohol-possibly mediated by alcohol cues and/or expectancies-in young adults with parental risk for mood/SUDs.

Free-access intravenous alcohol self-administration in social drinkers and individuals with alcohol use disorder: Evaluation of relationships with phosphatidylethanol and self-reported alcohol consumption

BACKGROUND

The free-access (FA) intravenous alcohol self-administration (IV-ASA) paradigm is an experimental approach that can identify modulators of alcohol consumption in humans. Moreover, the outcome measures of IV-ASA paradigms are associated with self-reported alcohol intake using the timeline follow-back method (TLFB). To evaluate how FA IV-ASA reflects drinking in real life, we examined the relationship between an objective marker of recent alcohol intake, phosphatidylethanol in blood (B-PEth), and TLFB and measures obtained during IV-ASA in individuals with alcohol use disorder (AUD) and social drinkers (SD). We also explored the associations between these measures and gut-brain peptides involved in AUD pathophysiology.

METHODS

Thirty-eight participants completed a laboratory session in which they self-administered alcohol intravenously. The safety limit was 200 mg%, and main outcomes were mean and peak breath alcohol concentrations (BrAC). Blood samples were drawn prior to IV-ASA and subjective alcohol effects were rated during the experiment.

RESULTS

The study sample comprised 24 SD and 14 participants with DSM-5 mild AUD. Although BrACs were not associated with B-PEth or TLFB in the full sample or AUD subgroup, there was an association with TLFB in SD. In both subgroups, BrACs were associated with alcohol craving but with differential timing. Total ghrelin levels were higher in AUD participants than in SD.

CONCLUSIONS

No associations between B-PEth levels and achieved BrACs were observed in the mild AUD group, the SD group, or the full sample. The ability for FA IV-ASA to reflect recent drinking was confirmed only for TLFB in SD, whereas there were no associations within the smaller subsample of participants with mild AUD or in the full sample. Further studies that include a larger AUD sample are warranted. The association of BrACs with craving for alcohol suggests that the IV-ASA method may be useful for assessing interventions that target craving. This could be explored by using the FA IV-ASA model to evaluate the effects on craving of approved pharmacotherapies for AUD.

Using naltrexone to validate a human laboratory test system to screen new medications for alcoholism (TESMA)- a randomized clinical trial

This registered clinical trial sought to validate a laboratory test system devised to screen medications for alcoholism treatment (TESMA) under different contingencies of alcohol reinforcement. Forty-six nondependent, but at least medium-risk drinkers were given the opportunity to earn intravenous infusions of ethanol, or saline, as rewards for work in a progressive-ratio paradigm. Work demand pattern and alcohol exposure dynamics were devised to achieve a gradual shift from low-demand work for alcohol (WFA) permitting quickly increasing breath alcohol concentrations (BrAC) to high-demand WFA, which could only decelerate an inevitable decrease of the previously earned BrAC. Thereby, the reward contingency changed, modeling different drinking motivations. The experiment was repeated after at least 7 days of randomized, double-blinded treatment with naltrexone, escalated to 50 mg/d, or placebo. Subjects treated with naltrexone reduced their cumulative WFA (cWFA) slightly more than participants receiving placebo. This difference was not statistically significant in the preplanned analysis of the entire 150 min of self-administration, i.e., our primary endpoint (p = 0.471, Cohen's d = 0.215). Naltrexone serum levels correlated with change in cWFA (r = -0.53; p = 0.014). Separate exploratory analyses revealed that naltrexone significantly reduced WFA during the first, but not the second half of the experiment (Cohen's d = 0.643 and 0.14, respectively). Phase-dependent associations of WFA with changes in subjective stimulation, wellbeing and desire for alcohol suggested that the predominant reinforcement of WFA was positive during the first phase only, and might have been negative during the second. We conclude that the TESMA is a safe and practical method. It bears the potential to quickly and efficiently screen new drugs for their efficacy to attenuate positively reinforced alcohol consumption. It possibly also provides a condition of negative reinforcement, and for the first time provides experimental evidence suggesting that naltrexone's effect might depend on reward contingency.

Haven't lost the positive feeling: a dose-response, oral alcohol challenge study in drinkers with alcohol use disorder

Models of addiction are based on neurobiological, behavioral, and pharmacological studies in animals, but translational support from human studies is limited. Studies are lacking in examining acute responses to alcohol in drinkers with alcohol use disorder (AUD), particularly in terms of relevant intoxicating doses and measurement of stimulating and rewarding effects throughout the breath alcohol concentration (BrAC) time curve. Participants were N = 60 AUD drinkers enrolled in the Chicago Social Drinking Project and examined in three random-order and blinded sessions for subjective and physiological responses to a beverage containing 0.0 g/kg, 0.8 g/kg, and 1.2 g/kg alcohol. BrAC in the alcohol sessions at 60 min was 0.09 g/dL and 0.13 g/dL, respectively. Both doses of alcohol produced significant biphasic effects on subjective measures of stimulation, euphoria, reward (liking and wanting), sedation, and neuroendocrine and cardiovascular factors. Increased pleasurable effects of alcohol were pronounced during the rising limb-to-peak BrAC and sedating effects emerged during the declining limb. Alcohol dose-dependently increased feel drug ratings and rewarding effects at peak BrAC or early declining limb, and physiological responses at the rising limb. Thus, rather than the notion of an overall tolerance, results show an alcohol response phenotype characterized by sensitivity to alcohol's stimulating, rewarding and physiological effects. The results of this study may aid in the conceptualization of alcohol addiction as a disorder characterized by the persistence of enhanced hedonic alcohol responses rather than chronic tolerance and reward deficiency.

Translating preclinical models of alcohol seeking and consumption into the human laboratory using intravenous alcohol self-administration paradigms

Preclinical models of alcohol use disorder (AUD) have advanced theoretical, mechanistic, and pharmacological study of the human condition. "Liking" and "wanting" behaviors reflect core processes underlying several models of AUD. However, the development and application of translational models of these preclinical approaches are at an incipient stage. The goal of this study was to examine how intravenous free-access and progressive-ratio, operant-response human alcohol self-administration paradigms can be used as translational human model parallels of preclinical "liking" and "wanting." Participants were 40 adults (mean age = 23.7, SD = 2.0; 45% female) of European descent who reported 12.6 drinking days (SD = 5.2) out of the previous 30 (average = 4.1 drinks per drinking day [SD = 1.7]). Individuals diverged in their alcohol self-administration behavior, such that free-access and progressive-ratio paradigm outcomes were not significantly correlated (p = 0.44). Free-access alcohol seeking was related to enjoying alcohol (p < 0.001), but not craving (p = 0.48), whereas progressive-ratio seeking at similar levels of alcohol exposure was related to craving (p = 0.02), but not enjoying (p = 0.30). Family history of alcoholism, venturesomeness traits, and disinhibition traits were unrelated (ps > 0.70) to preferred level of breath alcohol concentration (BrAC) in the free-access session, a measure of liking alcohol. Family history of alcoholism, disinhibition traits, and recent drinking history were significantly related (ps < 0.05) to alcohol seeking in the progressive-ratio paradigm, a measure of wanting alcohol. We conclude that intravenous alcohol self-administration paradigms show promise in modeling behaviors that characterize and parallel alcohol "liking" and "wanting" in preclinical models. These paradigms provide a translational link between preclinical methods and clinical trials.

Relationship between level of response to alcohol and acute tolerance

BACKGROUND

A low level of response (low LR) to alcohol correlates with the later development of alcohol-related problems. Although some of the underpinnings of LR are understood, little is known about the potential relationship between LR and acute tolerance. The current analyses tested the hypothesis that a low LR will be explained in part by more intense acute tolerance to alcohol during a drinking session.

METHODS

Data were generated through a reanalysis of data from 120 individuals who were 18- to 25-year-old, sex-matched pairs of low and high LR drinkers who at baseline did not meet criteria for an alcohol use disorder. Each subject participated in an oral alcohol challenge in which they consumed about 0.7 ml ethanol per kg and acute tolerance was measured as the differences in alcohol's effects at similar breath alcohol levels (BrACs) during the rising and falling breath alcohol concentration (BrAC) curve. Measures included aspects of the Subjective High Assessment Scale (SHAS) and body sway.

RESULTS

Contrary to our hypothesis, but similar to results with other alcohol measures, acute tolerance was significantly attenuated in low LR compared with high LR individuals on most SHAS scores. Neither LR group demonstrated acute tolerance to alcohol for sleepiness or body sway. Men and women did not differ on any of these measures.

CONCLUSION

These data do not support a role of acute tolerance in the low LR to alcohol as measured by subjective feelings of intoxication or body sway in these subjects, findings that were similar across males and females. In addition, consistent with the literature, the analyses demonstrated differences across measures such that acute tolerance was observed for most measures of subjective effects but not for body sway. Among the subjective effects, acute tolerance was observed for alcohol's intoxicating effect but not for feeling sleepy.

Acute Tolerance to the Analgesic Effects of Alcohol

OBJECTIVE

The goal of this study was to determine whether the acute analgesic effects of alcohol intake are moderated by acute alcohol tolerance, characterized by differing subjective and neurobehavioral effects of a given blood alcohol concentration (BAC) depending on whether BAC is rising or falling.

METHOD

Twenty-nine healthy drinkers (20 women) completed two laboratory sessions in which they consumed a study beverage: active alcohol (target BAC= .08 g/dl) and placebo. Acute alcohol tolerance was assessed by examining the main and interactive effects of beverage condition and assessment limb (ascending vs. descending) on quantitative sensory testing measures collected using slowly ramping heat stimuli and perceived relief ratings at comparable breath alcohol concentrations on the ascending and descending limbs.

RESULTS

BAC limb moderated the effect of condition on pain threshold, such that the threshold was significantly elevated in the alcohol condition on the ascending limb. The alcohol condition produced greater ratings of perceived pain relief than the placebo condition, and pain relief ratings were greater on the ascending versus descending limb of the BAC curve. Alcohol intake did not significantly affect pain tolerance or aftersensation ratings on either BAC limb.

CONCLUSIONS

This study provides initial experimental evidence that alcohol's analgesic and pain-relieving effects are subject to acute tolerance following acute alcohol intake. These findings suggest that self-medicating pain via alcohol intake may be associated with high-risk drinking topography, increasing the risk for alcohol-related consequences. Further research is needed to determine if these effects extend to the context of clinical and chronic pain.

Acute Tolerance to the Analgesic Effects of Alcohol

OBJECTIVE

The goal of this study was to determine whether the acute analgesic effects of alcohol intake are moderated by acute alcohol tolerance, characterized by differing subjective and neurobehavioral effects of a given blood alcohol concentration (BAC) depending on whether BAC is rising or falling.

METHOD

Twenty-nine healthy drinkers (20 women) completed two laboratory sessions in which they consumed a study beverage: active alcohol (target BAC= .08 g/dl) and placebo. Acute alcohol tolerance was assessed by examining the main and interactive effects of beverage condition and assessment limb (ascending vs. descending) on quantitative sensory testing measures collected using slowly ramping heat stimuli and perceived relief ratings at comparable breath alcohol concentrations on the ascending and descending limbs.

RESULTS

BAC limb moderated the effect of condition on pain threshold, such that the threshold was significantly elevated in the alcohol condition on the ascending limb. The alcohol condition produced greater ratings of perceived pain relief than the placebo condition, and pain relief ratings were greater on the ascending versus descending limb of the BAC curve. Alcohol intake did not significantly affect pain tolerance or aftersensation ratings on either BAC limb.

CONCLUSIONS

This study provides initial experimental evidence that alcohol's analgesic and pain-relieving effects are subject to acute tolerance following acute alcohol intake. These findings suggest that self-medicating pain via alcohol intake may be associated with high-risk drinking topography, increasing the risk for alcohol-related consequences. Further research is needed to determine if these effects extend to the context of clinical and chronic pain.

Alcohol subjective responses in heavy drinkers: Measuring acute effects in the natural environment versus the controlled laboratory setting

BACKGROUND

For decades, laboratory alcohol challenges have been the "gold standard" for measuring individual differences in alcohol's subjective effects. However, these approaches are expensive and labor-intensive, making them impractical for large-scale use. This study examined the reliability and validity of a new high-resolution EMA (HR-EMA) ambulatory approach to assessing alcohol use and subjective responses in drinkers' natural environments.

METHODS

Participants were 83 young adult heavy social drinkers (58% male; mean ± SD age = 25.4 ± 2.6 years) who completed up to two smartphone-based, 3-h HR-EMA assessments of alcohol use and related subjective responses in their typical drinking environments. Reported alcohol consumption during the HR-EMA periods was used to calculate estimated blood alcohol concentration (eBAC). Subjective effects were measured using the Brief Biphasic Alcohol Effects Scale (B-BAES) and Drug Effects Questionnaire (DEQ). All participants also completed identical measures during a separate, 4 to 5-h laboratory session in which they received a 0.8 g/kg alcohol challenge.

RESULTS

Most natural environment drinking episodes (87%) met or exceeded the threshold for binge drinking (final mean eBAC = 0.12 g/dl). Associations between reported alcohol use and subjective responses on the B-BAES and DEQ were strongest earlier in the drinking events, with fair reliability of reported subjective effects across two HR-EMA episodes (intraclass correlation [ICC] range = 0.46-0.49). There was fair-to-good correspondence between HR-EMA- and laboratory-derived subjective responses (ICC range = 0.49-0.74), even after accounting for differences in alcohol consumption and drinking context. Reported stimulating and rewarding alcohol effects were higher in the ambulatory than laboratory setting, and vice versa for sedating effects.

CONCLUSIONS

This study supports the reliability and validity of smartphone-based HR-EMA to measure alcohol use and subjective responses in heavy drinkers' natural environments. These findings lend support to the use of ambulatory HR-EMA as a measure of alcohol subjective responses in risky drinkers when a laboratory protocol is not practical, feasible, or safe.

Effects of moderate alcohol levels on default mode network connectivity in heavy drinkers

BACKGROUND

It is well established that even moderate levels of alcohol affect cognitive functions such as memory, self-related information processing, and response inhibition. Nevertheless, the neural mechanisms underlying these alcohol-induced changes are still unclear, especially on the network level. The default mode network (DMN) plays an important role in memory and self-initiated mental activities; hence, studying functional interactions of the DMN may provide new insights into the neural mechanisms underlying alcohol-related changes.

METHODS

We investigated resting-state functional connectivity (rsFC) of the DMN in a cohort of 37 heavy drinkers at a breath alcohol concentration of 0.8 g/kg. Alcohol and saline were infused in a single-blind crossover design.

RESULTS

Intranetwork connectivity analyses revealed that participants showed significantly decreased rsFC of the right hippocampus and right middle temporal gyrus during acute alcohol exposure. Moreover, follow-up analyses revealed that these rsFC decreases were more pronounced in participants who reported stronger craving for alcohol. Exploratory internetwork connectivity analyses of the DMN with other resting-state networks showed no significant alcohol-induced changes, but suffered from low statistical power.

CONCLUSIONS

Our results indicate that acute alcohol exposure affects rsFC within the DMN. Functionally, this finding may be associated with impairments in memory encoding and self-referential processes commonly observed during alcohol intoxication. Future resting-state functional magnetic resonance imaging studies might therefore also investigate memory function and test whether DMN-related connectivity changes are associated with alcohol-induced impairments or craving.

Neuroendocrine Response to Exogenous Ghrelin Administration, Combined With Alcohol, in Heavy-Drinking Individuals: Findings From a Randomized, Double-Blind, Placebo-Controlled Human Laboratory Study

BACKGROUND

Accumulating evidence has established a role for the orexigenic hormone ghrelin in alcohol-seeking behaviors. Accordingly, the ghrelin system may represent a potential pharmacotherapeutic target for alcohol use disorder. Ghrelin modulates several neuroendocrine pathways, such as appetitive, metabolic, and stress-related hormones, which are particularly relevant in the context of alcohol use. The goal of the present study was to provide a comprehensive assessment of neuroendocrine response to exogenous ghrelin administration, combined with alcohol, in heavy-drinking individuals.

METHODS

This was a randomized, crossover, double-blind, placebo-controlled human laboratory study, which included 2 experimental alcohol administration paradigms: i.v. alcohol self-administration and i.v. alcohol clamp. Each paradigm consisted of 2 counterbalanced sessions of i.v. ghrelin or placebo administration. Repeated blood samples were collected during each session, and peripheral concentrations of the following hormones were measured: leptin, glucagon-like peptide-1, pancreatic polypeptide, gastric inhibitory peptide, insulin, insulin-like growth factor-1, cortisol, prolactin, and aldosterone.

RESULTS

Despite some statistical differences, findings were consistent across the 2 alcohol administration paradigms: i.v. ghrelin, compared to placebo, increased blood concentrations of glucagon-like peptide-1, pancreatic polypeptide, cortisol, and prolactin, both acutely and during the whole session. Lower levels of leptin and higher levels of aldosterone were also found during the ghrelin vs placebo session.

CONCLUSION

These findings, gathered from a clinically relevant sample of heavy-drinking individuals with alcohol use disorder, provide a deeper insight into the complex interplay between ghrelin and appetitive, metabolic, and stress-related neuroendocrine pathways in the context of alcohol use.

The Feasibility, Tolerability, and Safety of Administering a Very High Alcohol Dose to Drinkers with Alcohol Use Disorder

INTRODUCTION

There remains a paucity of research quantifying alcohol's effects in drinkers with alcohol use disorder (AUD), particularly responses to very high alcohol doses (≥0.8 g/kg). As drinkers with AUD frequently engage in very heavy drinking (8 to 10 drinks/occasion), doses of ≤0.8 g/kg may lack ecological validity. The present study examined the feasibility, tolerability, and safety of administering a very high alcohol dose (1.2 g/kg) to non-treatment-seeking AUD participants.

METHODS

Sixty-one young adult AUD drinkers enrolled in the Chicago Social Drinking Project and completed 3 laboratory sessions at which they consumed a beverage with 1.2, 0.8, and 0.0 g/kg alcohol. Physiological responses (vital signs, nausea and vomiting, breath alcohol concentrations [BrAC]) were monitored throughout the sessions. After each session, participants completed a next-day survey of substance use, engagement in risky behaviors, and related consequences.

RESULTS

Overall, the sample demonstrated good compliance with study procedures; 93% of participants adhered to presession alcohol abstinence requirements (indicated by BrAC < 0.003 g/dl), with no participants exhibiting serious alcohol withdrawal symptoms at arrival to study visits. The 1.2 g/kg alcohol dose achieved an expected mean peak BrAC of 0.13 g/dl at 60 minutes after drinking, which was well tolerated; the majority of the sample did not experience nausea (70%) or vomiting (93%), and dose effects on vital signs were not clinically significant. Finally, we demonstrated that the 1.2 g/kg alcohol dose is safe and not associated with postsession consequences, including reduced sleep time, atypical substance use, accidents or injuries, and severe hangovers.

CONCLUSION

Results support the feasibility, tolerability, and safety of administering a very high alcohol dose to young adult drinkers with AUD within the context of a well-validated laboratory alcohol challenge paradigm. Utilizing an alcohol dose more consistent with naturalistic drinking patterns may foster greater ecological validity of laboratory paradigms for persons with moderate to severe AUD.

An Exploratory Factor Analysis of the Stimulant, Sedative, and Affective Responses to Alcohol

BACKGROUND

Subjective response (SR) to acute alcohol reflects individual variance to the sensitivity of alcohol's pharmacological effects. It has been argued that measures of stimulation and sedation may not fully capture the full-range SR, with 2 novel domains proposed: high arousal negative and low arousal positive. While substantial progress has been made in the field of SR and alcohol use risk, it remains unknown how these novel domains correspond to traditional SR measures. Therefore, the current study examined the latent structure of traditional and novel SR measures at rising breath alcohol concentrations (BrACs) during alcohol administration.

METHODS

Heavy drinkers (n = 67; 36M/31F) participated in an intravenous alcohol administration. Questionnaires assessing stimulation, sedation, mood, valence and arousal, and craving were assessed at baseline and at BrACs of 20, 40, and 60 mg%. A series of exploratory factor analyses were conducted to examine the latent factor structure of SR at each time point. Correlations examined the association between the generated factors and measures of problematic alcohol use.

RESULTS

The analysis generated a 3-factor solution, consistent across all time points. The factors measured the following effects of SR: (i) stimulation and positive mood, (ii) sedation and aversive effects, and (iii) tension reduction. The tension reduction factor was most commonly associated with problematic alcohol use in this sample.

CONCLUSION

This study extends upon the literature evaluating the biobehavioral effects of alcohol by examining a novel combination of SR to alcohol measures. This study demonstrates that the proposed low arousal positive domain, which loaded onto the tension reduction factor, provides novel information not captured by previous SR measures. Going forward, studies of alcohol's subjective effects should use this dimensional approach to reduce multiple comparisons across a wide range of scales and to build a literature grounded on the underlying structure of SR as a translational phenotype for AUD.