Acute alcohol response phenotype in heavy social drinkers is robust and reproducible

Attenuated incubation of ethanol-induced conditioned taste aversion in a model of dependence

RATIONALE

Preclinical studies report attenuated ethanol-induced conditioned taste aversion (CTA) following chronic ethanol exposure, suggesting that tolerance develops to the aversive properties of ethanol. However, these studies are confounded by pre-exposure to the unconditioned stimulus (US; ethanol), which is well known to hinder conditioning.

OBJECTIVES

This study was designed to determine whether chronic ethanol exposure produces tolerance to the aversive properties of ethanol in the absence of a US pre-exposure confound.

METHODS

CTA was performed in adult male and female Long-Evans rats by pairing 0.1% ingested saccharin with an intraperitoneal injection of ethanol (1.5 or 2.0 g/kg) or saline. Rats were then rendered ethanol dependent using chronic intermittent ethanol (CIE) vapor exposure. Controls were exposed to room air (AIR). The effect of chronic ethanol on CTA expression and reconditioning were examined following vapor exposure.

RESULTS

Prior to vapor exposure, both sexes developed CTA to a comparable degree with 2.0 g/kg producing greater CTA than 1.5 g/kg ethanol. Following vapor exposure, AIR controls exhibited an increase in CTA magnitude compared to pre-vapor levels. This effect was largely absent in CIE-exposed rats. Re-conditioning after vapor exposure facilitated increased CTA magnitude to a similar degree in AIR- and CIE-exposed males. In contrast, CTA magnitude was unchanged by re-conditioning in females.

CONCLUSIONS

These data suggest that chronic ethanol does not facilitate tolerance to the aversive properties of ethanol but rather attenuates incubation of ethanol-induced CTA. Loss of CTA incubation suggests that CIE exposure disrupts circuits encoding aversion.

Attenuated incubation of ethanol-induced conditioned taste aversion in a model of dependence

Rationale

Preclinical studies report attenuated ethanol-induced conditioned taste aversion (CTA) following chronic ethanol exposure, suggesting that tolerance develops to the aversive properties of ethanol. However, these studies are confounded by pre-exposure to the unconditioned stimulus (US; ethanol), which is well known to hinder conditioning.

Objectives

This study was designed to determine whether chronic ethanol exposure produces tolerance to the aversive properties of ethanol in the absence of a US pre-exposure confound.

Methods

CTA was performed in adult male and female Long-Evans rats by pairing 0.1% ingested saccharin with an intraperitoneal injection of ethanol (1.5 or 2.0 g/kg) or saline. Rats were then rendered ethanol dependent using chronic intermittent ethanol (CIE) vapor exposure. Controls were exposed to room air (AIR). The effect of chronic ethanol on CTA expression and reconditioning were examined following vapor exposure.

Results

Prior to vapor exposure, both sexes developed CTA to a comparable degree with 2.0 g/kg producing greater CTA than 1.5 g/kg ethanol. Following vapor exposure, AIR controls exhibited an increase in CTA magnitude compared to pre-vapor levels. This effect was absent in CIE-exposed rats. These group differences were eliminated upon re-conditioning after vapor exposure.

Conclusions

These data suggest that chronic ethanol does not facilitate tolerance to the aversive properties of ethanol but rather, attenuates incubation of ethanol-induced CTA. Loss of CTA incubation suggests that CIE exposure disrupts circuits encoding aversion.

Synthetic Approaches to the New Drugs Approved During 2021

Each year, new drugs are introduced to the market, representing structures that have affinity for biological targets implicated in human diseases and conditions. These new chemical entities (NCEs), particularly small molecules and antibody-drug conjugates, provide insight into molecular recognition and serve as potential leads for the design of future medicines. This annual review is part of a continuing series highlighting the most likely process-scale synthetic approaches to 35 NCEs that were first approved anywhere in the world during 2021.

Holding your liquor: Comparison of alcohol-induced psychomotor impairment in drinkers with and without alcohol use disorder

BACKGROUND

Behavioral tolerance to alcohol underscores the widely accepted notion that individuals who regularly drink alcohol become less sensitive to its impairing effects. However, previous research assessing alcohol-induced impairment in humans has primarily focused on social drinkers. This has limited our understanding of the nature and extent of behavioral tolerance among heavier drinkers, such as those with alcohol use disorder (AUD).

METHODS

Data from three cohorts of the Chicago Social Drinking Project were evaluated to examine the acute effects of alcohol on psychomotor performance across the breath alcohol curve in light drinkers (LDs; n = 86), heavy drinkers (HDs; n = 208), and individuals with AUD (AUDs; n = 103). Before and at several intervals after ingesting either alcohol (0.8 g/kg, peak BrAC = 0.09 g/dL) or placebo in two random-order laboratory sessions, participants completed a test of fine motor coordination (Grooved Pegboard), a test of perceptual-motor processing (Digit Symbol Substitution Task), and a self-reported survey of perceived impairment. Sixty individuals with AUD completed a third session with a very high dose of alcohol (1.2 g/kg, peak BrAC = 0.13 g/dL).

RESULTS

The AUD and HD groups, relative to the LD group, perceived less impairment and demonstrated greater behavioral tolerance to an intoxicating dose of alcohol, exhibited by reduced peak impairment and a quicker return to baseline performance on psychomotor measures. Among individuals with AUD who consumed the very high dose, impairment was more than double that following the usual high dose, and it exceeded the impairment among LDs following the usual high dose.

CONCLUSIONS

In this sample of young adult drinkers, relative to the LD group, those with heavier drinking patterns (AUD and HD groups) showed greater behavioral tolerance to 0.8 g/kg alcohol, a dose typically associated with a binge drinking episode. However, when challenged with a very high alcohol dose commensurate with high-intensity drinking, individuals with AUD showed substantial psychomotor impairment.

Ghrelin Predicts Stimulant and Sedative Effects of Alcohol in Heavy Drinkers

AIM

The aim of this study was to examine the relationship between ghrelin levels and the subjective effects of alcohol in heavy drinkers, and to compare them to healthy controls.

METHODS

Ghrelin levels were collected as part of two laboratory studies. Both groups received either IV infusion of saline or high dose of alcohol (100 mg%). In the study of heavy drinkers, ghrelin was gathered on all subjects, but data was analyzed only for participants who received placebo (N=12). Healthy controls (N=20) came from another study that collected data on family history. Ghrelin levels and measures of alcohol effects (BAES, VAS, NDS, YCS [see manuscript for details]) were collected at 4 timepoints: baseline, before infusion, during infusion and after infusion.

RESULTS

IV alcohol significantly reduced ghrelin levels and higher fasting ghrelin levels were associated with more intense subjective alcohol effects. There were no differences in fasting ghrelin levels or subjective effects between heavy drinkers and controls. However, while both groups showed similar decline in ghrelin levels following alcohol infusion, on the placebo day, ghrelin levels in the healthy subjects increased significantly and exponentially over time while for the heavy drinkers ghrelin levels remained flat.

CONCLUSIONS

Our findings support the role of ghrelin in reward mechanisms for alcohol. Contrary to others, we found no differences in fasting ghrelin levels or subjective experiences of alcohol between heavy drinkers and healthy controls. However, the group differences on the IV placebo day may be a possible indication of ghrelin abnormalities in heavy drinkers.

The impact of alcohol use on the quality of cardiopulmonary resuscitation among festival attendees: A prespecified analysis of a randomised trial

BACKGROUND

Cardiac arrests often occur in public places, but despite the undisputed impact of bystander CPR, it is debated whether one should act as a rescuer after alcohol consumption due to the perceived adverse effects. We provide the first objective data on the impact of alcohol levels on CPR-skills.

METHODS

Pre-specified analysis of a randomised study at the Lowlands music festival (August 2019, the Netherlands) on virtual reality vs face-to-face CPR-training. Participants with an alcohol level ≥ 0.5‰ (WHO-endorsed cut-off for traffic participation) were eligible provided they successfully completed a tandem gait test. We studied alcohol levels (AL, ‰) in relation to CPR-quality (compression depth and rate) and CPR-scenario performance.

RESULTS

Median age of the 352 participants was 26 (22-31) years, 56% were female, with n = 214 in Group 1 (AL = 0‰), n = 85 in Group 2 (AL = 0-0.5‰) and n = 53 in Group 3 (AL ≥ 0.5‰). There were no significant differences in CPR-quality (depth: 57 [49-59] vs 57 [51-60] vs 55 mm [47-59], p = 0.16; rate: 115 [104-121] vs 114 [106-122] vs 111 min^-1 [95-120], p = 0.19). There were no significant correlations between alcohol level and compression depth (Spearman's rho -0.113, p = 0.19) or rate (Spearman's rho -0.073, p = 0.39). CPR-scenario performance scores (maximum 13) were not different between groups (12 (9-13) vs 12 (9-13) vs 11 (9-13), p = 0.80).

CONCLUSION

In this study on festival attendees, we found no association between alcohol levels and CPR-quality or scenario performance shortly after training.

TRIAL REGISTRATION

Lowlands Saves Lives is registered on https://www.

CLINICALTRIALS

gov (NCT04013633).

Effect of intravenous ghrelin administration, combined with alcohol, on circulating metabolome in heavy drinking individuals with alcohol use disorder

BACKGROUND

Ghrelin may influence several alcohol-related behaviors in animals and humans by modulating central and/or peripheral biological pathways. The aim of this exploratory analysis was to investigate associations between ghrelin administration and the human circulating metabolome during alcohol exposure in nontreatment seeking, heavy drinking individuals with alcohol use disorder (AUD).

METHODS

We used serum samples from a randomized, crossover, double-blind, placebo-controlled human laboratory study with intravenous (IV) ghrelin or placebo infusion in two experiments. During each session, participants received a loading dose (3 µg/kg) followed by continuous infusion (16.9 ng/kg/min) of acyl ghrelin or placebo. The first experiment included an IV alcohol self-administration (IV-ASA) session and the second experiment included an IV alcohol clamp (IV-AC) session, both with the counterbalanced infusion of ghrelin or placebo. Serum metabolite profiles were analyzed from repeated blood samples collected during each session.

RESULTS

In both experiments, ghrelin infusion was associated with an altered serum metabolite profile, including significantly increased levels of cortisol (IV-ASA q-value = 0.0003 and IV-AC q < 0.0001), corticosterone (IV-ASA q = 0.0202 and IV-AC q < 0.0001), and glycochenodeoxycholic acid (IV-ASA q = 0.0375 and IV-AC q = 0.0013). In the IV-ASA experiment, ghrelin infusion increased levels of cortisone (q = 0.0352) and fatty acids 18:1 (q = 0.0406) and 18:3 (q = 0.0320). Moreover, in the IV-AC experiment, ghrelin infusion significantly increased levels of glycocholic acid (q < 0.0001) and phenylalanine (q = 0.0458).

CONCLUSION

IV ghrelin infusion, combined with IV alcohol administration, was associated with increases in the circulating metabolite levels of corticosteroids and glycine-conjugated bile acids, among other changes. Further research is needed to understand the role that metabolomic changes play in the complex interaction between ghrelin and alcohol.

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.

Eye Tracking Studies Exploring Cognitive and Affective Processes among Alcohol Drinkers: a Systematic Review and Perspectives

Acute alcohol intoxication and alcohol use disorders are characterized by a wide range of psychological and cerebral impairments, which have been widely explored using neuropsychological and neuroscientific techniques. Eye tracking has recently emerged as an innovative tool to renew this exploration, as eye movements offer complementary information on the processes underlying perceptive, attentional, memory or executive abilities. Building on this, the present systematic and critical literature review provides a comprehensive overview of eye tracking studies exploring cognitive and affective processes among alcohol drinkers. Using PRISMA guidelines, 36 papers that measured eye movements among alcohol drinkers were extracted from three databases (PsycINFO, PubMed, Scopus). They were assessed for methodological quality using a standardized procedure, and categorized based on the main cognitive function measured, namely perceptive abilities, attentional bias, executive function, emotion and prevention/intervention. Eye tracking indexes showed that alcohol-related disorders are related to: (1) a stable pattern of basic eye movement impairments, particularly during alcohol intoxication; (2) a robust attentional bias, indexed by increased dwell times for alcohol-related stimuli; (3) a reduced inhibitory control on saccadic movements; (4) an increased pupillary reactivity to visual stimuli, regardless of their emotional content; (5) a limited visual attention to prevention messages. Perspectives for future research are proposed, notably encouraging the exploration of eye movements in severe alcohol use disorders and the establishment of methodological gold standards for eye tracking measures in this field.

Alcohol Sensitivity as an Endophenotype of Alcohol Use Disorder: Exploring Its Translational Utility between Rodents and Humans

Alcohol use disorder (AUD) is a complex, chronic, relapsing disorder with multiple interacting genetic and environmental influences. Numerous studies have verified the influence of genetics on AUD, yet the underlying biological pathways remain unknown. One strategy to interrogate complex diseases is the use of endophenotypes, which deconstruct current diagnostic categories into component traits that may be more amenable to genetic research. In this review, we explore how an endophenotype such as sensitivity to alcohol can be used in conjunction with rodent models to provide mechanistic insights into AUD. We evaluate three alcohol sensitivity endophenotypes (stimulation, intoxication, and aversion) for their translatability across human and rodent research by examining the underlying neurobiology and its relationship to consumption and AUD. We show examples in which results gleaned from rodents are successfully integrated with information from human studies to gain insight in the genetic underpinnings of AUD and AUD-related endophenotypes. Finally, we identify areas for future translational research that could greatly expand our knowledge of the biological and molecular aspects of the transition to AUD with the broad hope of finding better ways to treat this devastating disorder.

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.

Predictors of Increases in Alcohol Problems and Alcohol Use Disorders in Offspring in the San Diego Prospective Study

BACKGROUND

The 35-year-long San Diego Prospective Study documented 2-fold increases in alcohol problems and alcohol use disorders (AUDs) in young-adult drinking offspring compared to rates in their fathers, the original probands. The current analyses use the same interviews and questionnaires at about the same age in members of the 2 generations to explore multiple potential contributors to the generational differences in adverse alcohol outcomes.

METHODS

Using data from recent offspring interviews, multiple cross-generation differences in characteristics potentially related to alcohol problems were evaluated in 3 steps: first through direct comparisons across probands and offspring at about age 30; second by backward linear regression analyses of predictors of alcohol problems within each generation; and finally third through R-based bootstrapped linear regressions of differences in alcohol problems in randomly matched probands and offspring.

RESULTS

The analyses across the analytical approaches revealed 3 consistent predictors of higher alcohol problems in the second generation. These included the following: (i) a more robust relationship to alcohol problems for offspring with a low level of response to alcohol; (ii) higher offspring values for alcohol expectancies; and (iii) higher offspring impulsivity.

CONCLUSIONS

The availability of data across generations offered a unique perspective for studying characteristics that may have contributed to a general finding in the literature of substantial increases in alcohol problems and AUDs in recent generations. If replicated, these results could suggest approaches to be used by parents, healthcare workers, insurance companies, and industry in their efforts to mitigate the increasing rates of alcohol problems in younger generations.

Relationships between generalized impulsivity and subjective stimulant and sedative responses following alcohol administration

Impulsivity and subjective response (SR) to alcohol (i.e., individual differences in sensitivity to pharmacologic alcohol effects) are both empirically supported risk factors for alcohol use disorder; however, these constructs have been infrequently studied as related risk factors. The present investigation examined a self-report measure of impulsivity (i.e., the Barratt Impulsiveness Scale, Version 11) in relation to acute alcohol effects (i.e., stimulant and sedative SR). Participants came from 2 cohorts of the Chicago Social Drinking Project. Heavy and light drinkers from Cohort 1 (n = 156) and heavy social drinkers from Cohort 2 (n = 104) were examined using identical laboratory protocols following oral alcohol administration using a within-subject, double-blind, placebo-controlled laboratory study design. Self-reported impulsivity and, for comparison purposes, sensation seeking were measured at baseline, and SR was measured once prior to and 4 times following alcohol administration. More impulsive light, but not heavy, drinkers reported heightened stimulant SR following alcohol administration. High impulsive, light drinkers reported stimulant SR at a magnitude similar to that for heavy drinkers, whereas low impulsive, light drinkers reported limited stimulant SR. The interaction between impulsivity and sensation seeking did not statistically predict stimulant SR, and overall, impulsivity was a stronger predictor than was sensation seeking. However, impulsivity was not statistically predictive of dampened sedative SR among light or heavy drinkers. These findings partially replicate and extend the recent literature linking self-reported impulsivity to heightened stimulant SR from alcohol. Future directions include longitudinal studies and research relating multiple facets of impulsivity to SR. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The dopamine transporter VNTR polymorphism moderates the relationship between acute response to alcohol and future alcohol use disorder symptoms

Alcohol use disorder (AUD) is a genetically influenced disease with peak onset in young adulthood. Identification of factors that predict whether AUD symptoms will diminish or persist after young adulthood is a critical public health need. King and colleagues previously reported that acute response to alcohol predicted future AUD symptom trajectory. Genes associated with brain dopamine signaling, which underlies alcohol's rewarding effects, might influence this finding. This study analyzed whether variation at a variable number tandem repeat polymorphism in DAT1/SLC6A3, the gene encoding the dopamine transporter, moderated the predictive relationships between acute response to alcohol and future AUD symptoms among participants enrolled in the Chicago Social Drinking Project (first two cohorts). Heavy-drinking young adults (N = 197) completed an alcohol challenge, in which acute response (liking, wanting, stimulation, and sedation) was measured. Alcohol use disorder symptoms were assessed over the following 6 years. DAT1 genotype significantly moderated the interactions between follow-up time and alcohol liking (P = 0.006) and wanting (P = 0.006) in predicting future AUD symptoms. These predictive effects were strongest among participants who carried the DAT1 9-repeat allele, previously associated with enhanced striatal dopamine tone relative to the 10-repeat allele. Exploratory analyses indicated that DAT1 effects on the relationship between alcohol liking and AUD symptoms appeared stronger for females (n = 79) than males (n = 118) (P = 0.0496). These data suggest that heavy-drinking DAT1 9-repeat allele carriers who display high alcohol-induced reward in young adulthood may be predisposed to persistent AUD symptoms and support combining genotypic and phenotypic information to predict future AUD risk.

The Interplay Between Subjective Response to Alcohol, Craving, and Alcohol Self-Administration in the Human Laboratory

BACKGROUND

Despite a rich literature on human laboratory paradigms of subjective response (SR) to alcohol, craving for alcohol, and alcohol self-administration, few studies have examined the interplay across these 3 constructs. The present study addresses this gap in the literature by examining the interplay between SR, craving, and self-administration in the human laboratory.

METHODS

Data were culled from a medication study (NCT02026011) in which heavy drinking participants of East Asian ancestry completed 2 double-blinded and counterbalanced experimental sessions. In each experimental session, participants received a priming dose of intravenous (IV) alcohol to a target breath alcohol concentration (BrAC) of 0.06 g/dl and measures of SR (stimulation and sedation) and alcohol craving were collected across rising BrACs. The IV alcohol challenge was immediately followed by a 1-hour alcohol self-administration period.

RESULTS

Mixed model analyses found a positive and significant relationship between the slope of stimulation and the slope of craving during the alcohol challenge. The relationship between sedation and craving, however, was not significant. The slope of craving during the alcohol challenge significantly predicted a higher number of mini-drinks consumed and lower latency to first drink. Further, mediation analyses found that craving was a significant mediator of the relationship between stimulation and total number of mini-drinks consumed, but the same pattern was not found for sedation.

CONCLUSIONS

Insofar as alcohol self-administration represents the end point of interest for a host of experimental and clinical research questions, the present study suggests that alcohol craving represents a more proximal predictor of self-administration than measures of alcohol-induced stimulation. It is recommended that human laboratory models interpret measures of SR and craving in light of their relative predictive utility for drinking outcomes.

The role of alcohol response phenotypes in the risk for alcohol use disorder

Heavy alcohol use is pervasive and one of our most significant global health burdens. Early theories posited that certain alcohol response phenotypes, notably low sensitivity to alcohol ('low-level response') imparts risk for alcohol use disorder (AUD). However, other theories, and newer measures of subjective alcohol responses, have challenged that contention and argued that high sensitivity to some alcohol effects are equally important for AUD risk. This study presents results of a unique longitudinal study in 294 young adult non-dependent drinkers examined with alcohol and placebo testing in the laboratory at initial enrolment and repeated 5 years later, with regular follow-up intervals assessing AUD (trial registration: http://clinicaltrials.gov/ct2/show/NCT00961792). Findings showed that alcohol sedation was negatively correlated with stimulation across the breath alcohol curve and at initial and re-examination testing. A higher rather than lower alcohol response phenotype was predictive of future AUD. The findings underscore a new understanding of factors increasing vulnerability to AUD.

Interneuronal δ-GABAA receptors regulate binge drinking and are necessary for the behavioral effects of early withdrawal

Extensive evidence points to a role for GABAergic signaling in the amygdala in mediating the effects of alcohol, including presynaptic changes in GABA release, suggesting effects on GABAergic neurons. However, the majority of studies focus solely on the effects of alcohol on principal neurons. Here we demonstrate that δ-GABA_ARs, which have been suggested to confer ethanol sensitivity, are expressed at a high density on parvalbumin (PV) interneurons in the basolateral amygdala (BLA). Thus, we hypothesized that δ-GABA_ARs on PV interneurons may represent both an initial pharmacological target for alcohol and a site for plasticity associated with the expression of various behavioral maladaptations during withdrawal from binge drinking. To investigate this, we used a mouse model of voluntary alcohol intake (Drinking-in-the-Dark-Multiple Scheduled Access) to induce escalating heavy binge drinking and anxiety-like behavior in mice. This pattern of intake was associated with increased δ protein expression on parvalbumin positive interneurons in both the BLA and hippocampus. Loss of δ-GABA_ARs specifically in PV interneurons (PV:δ^-/-) increased binge drinking behavior, reduced sensitivity to alcohol-induced motor incoordination, enhanced sensitivity to alcohol-induced hyperlocomotion and blocked the expression of withdrawal from binge drinking. This study is the first to demonstrate a role for δGABA_ARs specifically in PV-expressing interneurons in modulating binge alcohol intake and withdrawal-induced anxiety.

Striatal activity correlates with stimulant-like effects of alcohol in healthy volunteers

Individuals who experience greater stimulation and less sedation from alcohol are at increased risk for alcohol-related problems. However, little is known regarding the neurobiological mechanisms underlying subjective response to alcohol. The current study examined the degree to which alcohol-induced brain activation correlates with ratings of stimulation and sedation, using a within-subjects, double-blind, placebo-controlled design. Participants (N = 34 healthy adults with no history of alcohol use disorder) completed three sessions: a calibration session to determine the duration of infusion needed to bring the breath alcohol to 80 mg/dl for each subject, and two counterbalanced fMRI sessions with placebo and alcohol administration. During the fMRI sessions, participants underwent 50 min scans, which included a 10 min baseline period, the IV infusion period needed to bring breath alcohol concentration (BrAC) to a peak 80 mg/dl (on the alcohol session), followed by a post-peak decline period. Participants rated their subjective stimulation and sedation at regular intervals throughout the scan. A priori VOI analyses showed that the time course of stimulation correlated with BOLD signal in the striatum. The time course of sedation did not correlate with BOLD signal in any VOIs. There were no correlations in primary visual cortex, which served as a control. These findings are the first to show that alcohol effects in the striatum are linked to the positive, stimulant-like effects of the drug and advance our understanding of the neurobiological mechanisms underlying individual differences in subjective responses to alcohol, and more broadly, risk for alcohol use disorders.

A Critical Review of Methods and Results in the Search for Genetic Contributors to Alcohol Sensitivity

Attributes of alcohol sensitivity are present before alcohol use disorders (AUDs) develop, they predict those adverse alcohol outcomes, are familial in nature, and many are heritable. Whether measured by alcohol challenges or retrospective reports of numbers of drinks required for effects, alcohol sensitivity reflects multiple phenotypes, including low levels of alcohol response and alcohol-related stimulation. Identification of genes that contribute to alcohol sensitivity could help identify individuals carrying risks for AUDs through their alcohol responses for whom early intervention might mitigate their vulnerability. Such genes could also improve understanding of biological underpinnings of AUDs, which could lead to new treatment approaches. However, the existing literature points to a wide range of genetic mechanisms that might contribute to alcohol responses, and few such genetic findings have been widely replicated. This critical review describes the potential impact of the diverse methods used to study sensitivity on the diversity of genetic findings that have been reported, places the genetic variants mentioned in the literature into broader categories rather than isolated results, and offers suggestions regarding how to advance the field by interpreting findings in light of the methods used to select research subjects and to measure alcohol sensitivity. To date, the most promising results have been for GABA, glutamate, opioid, dopamine, serotonin, and cholinergic system genes. The more gene variants that can be identified as contributors to sensitivity the better future gene screening platforms or polygenic scores are likely to be.

Intra- and Interindividual Variability in the Behavioral, Affective, and Perceptual Effects of Alcohol Consumption in a Social Context

BACKGROUND

We examined the influence of interindividual differences in alcohol use on the intraindividual associations of drinking occurrence with interpersonal behaviors, affect, and perceptions of others during naturally occurring social interactions.

METHODS

For 14 consecutive days, 219 psychology freshmen (55% female; M_age  = 20.7 years, SD = 2.18) recorded their behaviors, affect, and perceptions in social interactions soon after an interpersonal event occurred. Interpersonal behaviors and perceptions were assessed in terms of dominance-submissiveness and agreeableness-quarrelsomeness. Participants also reported the number of alcoholic drinks consumed within 3 hours of each interaction. We considered the intraindividual associations of (i) having a drinking episode and (ii) the number of drinks during an episode with behaviors, affect, and perceptions and examined interindividual differences in drinking frequency and intensity during social interactions as potential moderators of these associations.

RESULTS

Social drinking frequency and intensity moderated the associations between drinking episode and behaviors, affect, and perceptions in social interactions. During a drinking episode, more frequent social drinkers perceived others as more dominant than less frequent social drinkers. During a drinking episode in which more alcohol was consumed than usual, more frequent social drinkers also reported behaving more dominantly and experiencing less pleasant affect.

CONCLUSIONS

As more frequent social drinkers had different interpersonal responses to drinking than less frequent social drinkers, including when they had consumed larger amounts of alcohol than usual, our results suggest a differential susceptibility to the effects of alcohol during naturally occurring social interactions among drinkers with varying drinking frequency.

A paradigm for examining stress effects on alcohol-motivated behaviors in participants with alcohol use disorder

Although epidemiological research has shown an increase in drinking following stressors and trauma, limited paradigms have been validated to study the relationship between stress and drinking in the human laboratory. The current study developed a progressive ratio (PR) operant procedure to examine the effects of psychosocial stress on alcohol craving and several alcohol-motivated behaviors in persons with alcohol use disorder. Current heavy, nontreatment-seeking drinkers (N = 30) were media-recruited and completed a comprehensive assessment of recent drinking, mood and health. Participants were admitted to the clinical research unit and underwent 4-day, physician-monitored alcohol abstinence. On days 4 and 5, participants underwent the Trier Social Stress Test or a neutral session in random order followed by the alcohol-motivated response (AMR) procedure in which subjects worked for money or alcohol under a PR operant procedure. Subjects received earned money vouchers or alcohol at the conclusion of the session. The Trier Social Stress Test increased alcohol craving and rate of responding and decreased the number of changeovers between alcohol versus money reinforcers on the PR schedule. There was a positive relationship between alcohol craving and drinks earned during the stress session. This novel paradigm provides an experimental platform to examine motivation to drink without confounding by actual alcohol ingestion during the work session, thereby setting the stage for future studies of alcohol interventions.

Subjective alcohol responses in a cross-sectional, field-based study of adolescents and young adults: Effects of age, drinking level, and dependence/consequences

BACKGROUND

Adolescents are physically, cognitively, socially, and emotionally different than adults in ways that may partially explain why alcohol misuse typically develops during this period. Ample animal-science evidence and nascent ecological evidence points toward developmentally limited differences in sensitivity to alcohol's stimulatory and sedative effects. Field-based research methods were used to test for such age-related differences in a sample of adolescents through young adults. Potential moderating influences of estimated blood alcohol content (eBAC), as well as typical consumption and level of dependence/consequences were explored.

METHODS

Subjective alcohol responses were collected from 1,364 participants, aged 17 to 32 years, recruited outside of venues where drinking takes place in a small metropolitan bar district.

RESULTS

Self-reports of stimulatory response to alcohol were age-related, such that younger participants reported increased subjective stimulation at the time of data collection relative to older participants. Age-related differences in stimulatory responses were more pronounced at lower eBACs and among younger participants who typically drank more heavily. Stimulatory responses generally diminished among older than younger participants, although individuals with greater dependence/consequences consistently reported greater stimulation from drinking. Contrastingly, age, typical consumption, and dependence/consequences were not related to sedation in this sample.

CONCLUSIONS

This research provides cross-sectional evidence to support age-, consumption-, and dependence/consequences-related differences in stimulatory alcohol responses among adolescents and young adults assessed within a bar-area context. While cross-sectional, the results of this field-based study provide support for the theory that addiction liability is developmentally linked and associated, in part, with age-related differences in subjective alcohol responses.

Functional significance of subjective response to alcohol across levels of alcohol exposure

Pre-clinical neurobiological models of addiction etiology including both the allostatic model and incentive sensitization theory suggest that alcohol consumption among alcohol-dependent (AD) individuals will be dissociated from hedonic reward as positive reinforcement mechanisms wane in later stage dependence. The aims of this study are to test this claim in humans by examining the relationship between dimensions of subjective responses to alcohol (SR) and alcohol craving across levels of alcohol exposure. Non-treatment-seeking drinkers (n = 205) completed an i.v. alcohol challenge (final target breath alcohol concentration = 0.06 g/dl) and reported on SR and craving. Participants were classified as light-to-moderate drinkers (LMD), heavy drinkers (HD) or AD. Analyses examined group differences in SR and craving response magnitude, as well as concurrent and predictive associations between SR domains and craving. At baseline, LMD and AD reported greater stimulation than HD, which carried over post-alcohol administration. However, stimulation was dose-dependently associated with alcohol craving in HD only. Furthermore, lagged models found that stimulation preceded craving among HD only, whereas this hypothesized pattern of results was not observed for craving preceding stimulation. Sedation was also positively associated with craving, yet no group differences were observed. In agreement with the prediction of diminished positive reinforcement in alcohol dependence, this study showed that stimulation/hedonic reward from alcohol did not precede craving in AD, whereas stimulation was dose-dependently associated with and preceded craving among non-dependent HD.

Subjective Response to Alcohol as a Research Domain Criterion

BACKGROUND

Individual differences in the subjective experience of the pharmacological effects of alcohol have long been implicated in the likelihood that one will drink heavily and develop alcoholism. The theme of this conceptual review and perspective article is to synthesize the literature on subjective responses to alcohol and to set an agenda for the next generation of research in the area. Specifically, we contend that in order for subjective response to alcohol to play a prominent role in alcoholism research, it is critical that it be studied as a multimodal phenotype.

METHODS

First, we review the human research on subjective response to alcohol measured under controlled laboratory conditions and draw recommendations for the application of these findings to understanding alcoholism neurobiology in humans. Second, we highlight multimodal approaches, including studies of the genetic and neural substrates of individual differences in subjective response to alcohol. Third, we review treatment implications with a focus on subjective response to alcohol as an intervention target. Upon review of the research on subjective response to alcohol across levels of analyses, we provide recommendations for leveraging these phenotypes in a systematic and methodologically rigorous fashion that can address central questions about alcoholism etiology, disease progression, and personalized treatment.

DISCUSSION

The approach recommended herein is largely consistent with the Research Domain Criteria (RDoC) initiative across the National Institute of Mental Health. The defining feature of such domains is that they inform behavior yet be amenable to examination through multiple units of analysis, such as molecular, genetic, circuit-level, and behavioral measurements. To that end, we contend that subjective response to alcohol represents a behaviorally and biologically plausible phenotype upon which to build using the RDoC framework for understanding alcohol use disorder.

The natural expression of individual differences in self-reported level of response to alcohol during ecologically assessed drinking episodes

RATIONALE

Low sensitivity to alcohol is a well-established risk factor for alcohol use disorder (AUD). However, little is known about how the low sensitivity phenotype is expressed on a fine-grained, momentary level in drinkers' daily experience.

OBJECTIVES

The objective of the study is to evaluate individual differences in subjective states and appraisals of alcoholic beverages during the ascending limb of real-world drinking episodes.

METHODS

Social drinkers (N = 398) with varying degrees of alcohol sensitivity as indexed by the Self-Rating of the Effects of Alcohol form (SRE; Schuckit et al. in Addiction 92:979-988, 1997a) recorded diary entries over a 3-week monitoring period (2576 drinking episodes containing 6546 moments). Hierarchical linear modeling was used to evaluate whether individual differences in alcohol sensitivity predicted differing intra-episode estimated blood alcohol concentration (eBAC) trajectories, ratings of subjective states, and drink appraisals.

RESULTS

Lower self-reported alcohol sensitivity was associated with consuming "too much, too fast," as indicated by a steeper slope of ascending eBAC. In models adjusted for momentary eBAC level, participants reporting lower alcohol sensitivity at baseline showed blunted subjective intoxication and drink-contingent punishment.

CONCLUSIONS

The results suggest that low sensitivity to alcohol is associated with a blunting of some forms of subjective feedback (i.e., perceptions of intoxication and punishment) that might typically encourage drinking restraint. This may 'tip the scales' toward excess consumption and could help to explain why a low alcohol sensitivity forecasts AUD.

A Prospective 5-Year Re-examination of Alcohol Response in Heavy Drinkers Progressing in Alcohol Use Disorder

BACKGROUND

The main neurobiological theories of the development of addiction, including tolerance, sensitization, incentive-sensitization, and allostasis, have not been tested in longitudinal human alcohol response research. To address this issue, we conducted the first controlled prospective investigation of subjective and neuroendocrine responses to alcohol measured over a 5-year interval in at-risk young adult heavy drinkers (HD) and light drinker control subjects.

METHODS

Participants were 156 individuals, 86 heavy drinkers and 70 light drinkers, undergoing an initial oral alcohol challenge testing (.8 g/kg alcohol vs. placebo) and an identical re-examination testing 5 to 6 years later. Alcohol use disorder (AUD) symptoms and drinking behaviors were assessed in the interim follow-up period.

RESULTS

At re-examination, HD continued to exhibit higher sensitivity on alcohol's stimulating and rewarding effects with lower sensitivity to sedative effects and cortisol reactivity, relative to light drinkers. In HD with high AUD symptom trajectories over follow-up, heightened alcohol stimulation and reward persisted at re-examination. HD with low AUD symptoms showed reduced alcohol stimulation over time and lower reward throughout compared with the HD with high and intermediate AUD symptoms.

CONCLUSIONS

Results support the early stage phase of the allostasis model, with persistently heightened reward sensitivity and stimulation in heavy drinkers exhibiting AUD progression in early mid-adulthood. While there are multiple pathways to development of a disorder as complex as AUD, maintenance of alcohol stimulatory and rewarding effects may play an important role in the continuation and progression of alcohol addiction.

Current insights into the mechanisms and development of treatments for heavy drinking cigarette smokers

There is a strong association between cigarette smoking and alcohol use at the epidemiological, behavioral, and molecular levels, and this co-use creates substantial impediments to smoking cessation among smokers who are also heavy drinkers. Compared with individuals who only smoke, those who both drink and smoke heavily experience more severe health consequences and have greater difficulty in quitting smoking. During smoking abstinence, greater alcohol use is associated with decreased odds of smoking cessation, and smokers are substantially more likely to experience a smoking lapse during drinking episodes. As heavy drinking smokers are less responsive to the currently available pharmacological treatments, this subgroup of high-risk substance users possesses a unique clinical profile and treatment needs. Thus, treatment development for heavy drinking smokers represents a significant and understudied research area within the field of smoking cessation. This review will briefly describe findings from epidemiological, behavioral, and molecular studies illustrating alcohol and tobacco co-use and identify how the behavioral and neurobiological mechanisms underlying the interaction of alcohol and nicotine may inform the development of targeted treatments for this unique population of smokers.

Integrating alcohol response feedback in a brief intervention for young adult heavy drinkers who smoke: A pilot study

BACKGROUND

More effective approaches are needed to enhance drinking and other health behavior (e.g., smoking) outcomes of alcohol brief intervention (BI). Young adult heavy drinkers often engage in other health risk behaviors and show sensitivity to alcohol's stimulating and rewarding effects, which predicts future alcohol-related problems. However, standard alcohol BIs do not address these issues. The current pilot study tested the utility of including feedback on alcohol response phenotype to improve BI outcomes among young adult heavy drinkers who smoke (HDS).

METHODS

Thirty-three young adult (M±SD age=23.8±2.1 years) HDS (8.7±4.3 binge episodes/month; 23.6±6.3 smoking days/month) were randomly assigned to standard alcohol BI (BI-S; n=11), standard alcohol BI with personalized alcohol response feedback (BI-ARF; n=10), or a health behavior attention control BI (AC; n=11). Alcohol responses (stimulation, sedation, reward, and smoking urge) for the BI-ARF were recorded during a separate alcohol challenge session (.8g/kg). Outcomes were past-month drinking and smoking behavior assessed at 1- and 6-months post-intervention.

RESULTS

At 6-month follow-up, the BI-ARF produced significant reductions in binge drinking, alcohol-smoking co-use, drinking quantity and frequency, and smoking frequency, but not maximum drinks per occasion, relative to baseline. Overall, the BI-ARF produced larger reductions in drinking/smoking behaviors at follow-up than did the BI-S or AC.

CONCLUSIONS

Including personalized feedback on alcohol response phenotype may improve BI outcomes for young adult HDS. Additional research is warranted to enhance and refine this approach in a broader sample.

Factor Structure of Subjective Responses to Alcohol in Light and Heavy Drinkers

BACKGROUND

Subjective responses (SRs) to alcohol have been implicated in alcoholism etiology, yet less is known about the latent factor structure of alcohol responses. The aim of this study was to examine the factor structure of SR using a battery of self-report measures during a controlled alcohol challenge.

METHODS

Nontreatment seeking drinkers (N = 242) completed an intravenous alcohol challenge including the following SR measures: Biphasic Alcohol Effects Scale, Subjective High Assessment Scale, Profile of Mood States, Alcohol Urge Questionnaire, and single items assessing alcohol "Liking" and "Wanting." Ascending limb target breath alcohol concentrations were 0.02, 0.04, and 0.06, and descending limb target was 0.04 g/dl. Exploratory factor analyses were conducted separately on estimates of mean and dose responses on the ascending limb and on descending limb data. To examine the generalizability of this factor structure, these analyses were repeated in heavy drinkers (≥14 drinks/wk for men, ≥7 for women; n = 132) and light drinkers (i.e., nonheavy drinkers; n = 110).

RESULTS

In the full sample, a 4-factor solution was supported for ascending limb mean and dose responses and descending limb data representing the following SR domains: Stimulation/Hedonia, Craving/Motivation, Sedation/Motor Intoxication, and Negative Affect. This 4-factor solution was replicated in heavy drinkers. In light drinkers, however, SR was better summarized by a 3-factor solution where ascending mean and descending limb responses consisted of Stimulation/Hedonia, Craving/Motivation, and a general negative valence factor, and dose responses consisted of a general positive valence factor, Sedation/Motor Intoxication, and Negative Affect.

CONCLUSIONS

These findings suggest that SR represents a multifaceted construct with consistent factor structure across both ascending and descending limbs. Further, as drinking levels escalate, more defined Craving/Motivation and negative valence dimensions may emerge. Longitudinal studies examining these constructs are needed to further our understanding of SR as potentially sensitive to alcohol-induced neuroadaptation.

Subjective response as a consideration in the pharmacogenetics of alcoholism treatment

Currently available pharmacological treatments for alcoholism have modest efficacy and high individual variability in treatment outcomes, both of which have been partially attributed to genetic factors. One path to reducing the variability and improving the efficacy associated with these pharmacotherapies may be to identify overlapping genetic contributions to individual differences in both subjective responses to alcohol and alcoholism pharmacotherapy outcomes. As acute subjective response to alcohol is highly predictive of future alcohol related problems, identifying such shared genetic mechanisms may inform the development of personalized treatments that can effectively target converging pathophysiological mechanisms that convey risk for alcoholism. The focus of this review is to revisit the association between subjective response to alcohol and the etiology of alcoholism while also describing genetic contributions to this relationship, discuss potential pharmacogenetic approaches to target subjective response to alcohol in order to improve the treatment of alcoholism and examine conceptual and methodological issues associated with these topics, and outline future approaches to overcome these challenges.

Subjective response to alcohol and associated craving in heavy drinkers vs. alcohol dependents: an examination of Koob's allostatic model in humans

BACKGROUND

Koob's allostatic model of addiction emphasizes the transition from positive reinforcement to negative reinforcement as dependence develops. This study seeks to extend this well-established neurobiological model to humans by examining subjective response to alcohol (SR) as a biobehavioral marker of alcohol reinforcement. Specifically, this study examines (a) differential SR in heavy drinkers (HDs) vs. alcohol dependent individuals (ADs) and (b) whether HDs and ADs differ in terms of the association between SR and craving.

METHODS

Data was culled from two alcohol challenge studies, totalling 91 participants (oversampled on OPRM1 Asp40 carriers). Alcohol was administered intravenously and participants completed standard measures of SR and craving at BrAC's of 0.02, 0.04, and 0.06 g/dl. SR was modeled as a multi-dimensional construct consisting of stimulation, sedation, and tension relief.

RESULTS

ADs reported significantly higher sedation and craving initially and exhibited a blunted response to alcohol along escalating BrACs. ADs exhibited greater initial tension but did not differ from HDs in tension reduction across rising BrACs. Further, alcohol-induced stimulation was associated with alcohol craving to a significantly greater degree in HDs, as compared to ADs.

CONCLUSIONS

This study provides initial evidence that HDs and ADs differ in their subjective experience of alcohol and in the association between dimensions of SR and craving for alcohol. Hypotheses derived from the allostatic model were partially supported, such that, while ADs and HDs did not differ on stimulation response, there was a relative dissociation between positive reinforcement and craving in ADs as compared to HDs.