Acute alcohol intake alters resting state functional connectivity of nucleus accumbens with pain-related corticolimbic structures

Ventral prefrontal network response to alcohol in young adults with bipolar disorder: a within-subject randomized placebo-controlled alcohol administration study

Bipolar disorder co-occurs with alcohol use disorder at a rate 3-5 times higher than the general population. We recently reported that individuals with bipolar disorder differ in the positive stimulating and anxiolytic effects of alcohol compared with healthy peers. This study used a randomized, placebo-controlled, cross-over, within-subject alcohol administration design to investigate neurobiological mechanisms within ventral prefrontal cortical (vPFC) systems that may underlie altered sensitivity to alcohol in bipolar disorder (NCT04063384). Forty-seven young adults (n = 23 with bipolar disorder, 64% women) completed clinical assessment and two beverage administration sessions (alcohol and placebo, counter-balanced). Participants were dosed to 0.08 g% breath alcohol concentration during the alcohol condition and completed measures of subjective response to alcohol and an emotional processing fMRI task during the ascending limb. Timing during the placebo condition mirrored the alcohol session. Acute alcohol was associated with reduced functional connectivity between the insula - subcallosal cingulate cortex, and increased connectivity between the left nucleus accumbens - ventromedial PFC in bipolar disorder, but with no change in functional connectivity between these regions in healthy peers. Alcohol-related increases in nucleus accumbens - ventromedial PFC functional connectivity was associated with greater positive stimulating effects of alcohol in bipolar disorder and heavier recent alcohol use. Results suggest vPFC brain systems respond differently to acute alcohol during emotional processing in young adults with bipolar disorder compared with healthy peers, and that vPFC system responses relate to the subjective experience of intoxication and recent alcohol use.

Neural and Psychosocial Mechanisms Underlying Alcohol Use and Pain Interactions: Overview of Current Evidence and Future Directions

Purpose of Review

A growing body of research indicates bidirectional associations between alcohol use and pain. In this review, we highlight common neural and psychosocial mechanisms underlying pain and alcohol use and identify current gaps in the literature regarding alcohol/pain interactions. We also suggest future directions for the field moving forward, including more nuanced conceptualization of alcohol's negative reinforcing effects in the context of pain, broader use of clinically-relevant experimental pain induction modalities, and characterization of age, biological sex, gender, race, and ethnicity as moderators of pain/alcohol interactions.

Recent Findings

Acute alcohol intake has analgesic and negative-reinforcing effects in the context of pain, and chronic heavy alcohol use appears to increase risk for development of chronic pain. At the same time, pain, both acute and chronic, acts as a proximal antecedent for alcohol use and is associated with relapse risk for individuals in recovery from alcohol use disorder.

Summary

Although the links between alcohol use and pain are increasingly appreciated, significant gaps in understanding remain and systematic study of alcohol/pain interactions at all levels, including basic, preclinical, translational, and interventional, is needed.

Electroencephalography-Based Effects of Acute Alcohol Intake on the Pain Matrix

The effects of acute and chronic intakes of high doses of alcohol on pain perception are well known, ranging from short-term analgesic effects to long-term sensitization and polyneuropathies. The short-term analgesic effects of ethanol consumption on subjective pain perception have been well studied in the literature. Recent advances in neuroimaging allow for an insight into pain-related structures in the brain, fostering the mechanistic understanding of the processing of nociceptive input and pain. We aimed to utilize EEG, combined with standardized noxious mechanical/thermal stimulation and subjective pain testing, to research the effects of acute alcohol intake on nociceptive processing and pain perception. We recruited 12 healthy subjects in an unblinded cross-over study design and aimed at achieving a blood alcohol level of 0.1%. Our data revealed a significant reduction in subjective pain ratings to noxious thermal and mechanical stimuli after alcohol ingestion. Our EEG data revealed suppressing effects on the cortical structures responsible for processing pain, the "pain matrix". We conclude that in addition to its analgesic effects, as expressed by the reduction in subjective pain, alcohol has a further impact on the "pain matrix" and directly affects the salience to a nociceptive stimulus.

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.

Association of cerebellar and pre-motor cortex gray matter density with subjective intoxication and subjective response following acute alcohol intake

Acute alcohol intake produces subjective intoxication (SI) and response (SR; e.g., valanced stimulation and sedation), which has important implications for alcohol-related risk. Individuals who experience less SI may be more likely to engage in risky behaviors while drinking. Gray matter morphometry in brain regions underlying cognitive and affective processes may help to inform individual differences in subjective intoxication and response. The subjective effects of alcohol vary between limbs of the blood alcohol concentration (BAC) curve (i.e., whether BAC is rising or falling; acute tolerance). We examined the relationship between gray matter density (GMD) and SI/SR as a function of BAC limb. Healthy social drinkers (N = 89; 55 women) completed an alcohol challenge paradigm (target BAC = 0.08 g/dL) and structural magnetic resonance imaging (MRI). Participants completed measures of SR and SI on ascending and descending BAC limbs. Association between GMD and SI/SR on each limb were assessed using whole-brain, voxel-wise general linear models. GMD estimates were extracted from significant clusters. Differences in association of GMD and SI/SR between limbs were assessed using hierarchical regression. Significant associations of SI with GMD on the ascending limb were observed in the cerebellum. A significant association between SR and GMD on the descending limb were observed in the pre-motor cortex (BA6) and cerebellum. We identified common and unique associations among cerebellum and pre-central gyrus structures with SI and SR between BAC limbs. Functional imaging studies may further clarify unique dimensions of subjective alcohol effects linked to the observed structural associations.

Alcohol-induced changes in mesostriatal resting-state functional connectivity are linked to sensation seeking in young adults

BACKGROUND

Studies in animals and humans suggest that greater levels of sensation seeking and alcohol use are related to individual differences in drug-induced dopamine release. However, it remains unclear whether drug-induced alterations in the functional synchrony between mesostriatal regions are related to sensation seeking and alcohol use.

METHODS

In this within-subject masked-design study, 21-year-old participants (n = 34) underwent functional magnetic resonance imaging to measure ventral tegmental area (VTA) resting-state functional connectivity to the striatum after receiving alcohol (target blood alcohol concentration 0.08 g/dL) or placebo. Participants also completed the UPPS-P Impulsive Behavior Scale to assess sensation seeking, the Young Adult Alcohol Consequences Questionnaire, and self-reported patterns of alcohol and drug use.

RESULTS

Voxel-wise analyses within the striatum demonstrated that during the alcohol condition (compared with placebo) young adults had less connectivity between the VTA and bilateral caudate (p < 0.05 corrected). However, young adults exhibiting smaller alcohol-induced decreases or increases in VTA-left caudate connectivity reported greater sensation seeking.

CONCLUSION

These findings provide novel information about how acute alcohol impacts resting-state connectivity, an effect that may be driven by the complex pre and postsynaptic effects of alcohol on various neurotransmitters including dopamine. Further, alcohol-induced differences in VTA connectivity represent a plausible mechanistic substrate underlying sensation seeking.

Neural underpinnings of expecting alcohol: Placebo alcohol administration alters nucleus accumbens resting state functional connectivity

BACKGROUND

Using balanced placebo designs, seminal alcohol administration research has shown individuals' beliefs about whether they have consumed alcohol, irrespective of the actual presence of alcohol, can determine level of alcohol consumption and impact social behavior. Despite the known effect of expecting alcohol on drinking behavior, few studies have used the placebo manipulation to directly investigate the neural underpinnings of the expectancy-related effects that occur following perceived alcohol consumption in humans. The present paper examined placebo responses in the laboratory to better understand the neural basis for the psychological phenomenon of expectancies.

METHODS

As part of a larger within-subjects study design, healthy young adults (N = 22, agemean+SD=23 +1) completed resting state fMRI scans and measures of subjective response before and after consuming placebo beverages. Effect of placebo beverage consumption (pre- versus post-beverage consumption) on functional connectivity within prefrontal cortical networks was examined using the CONN Toolbox. Relations between perceived subjective response to alcohol with functional connectivity response following placebo beverage consumption were examined.

RESULTS

Compared to pre-beverage scan, placebo beverage consumption was associated with increased positive functional connectivity between right nucleus accumbens - ventromedial prefrontal cortex and subcallosal cingulate cortex (pFDR<0.05). Subjective ratings of intoxication (i.e., feeling 'drunk') positively correlated with placebo beverage-related increases in nucleus accumbens - subcallosal cingulate cortex functional connectivity.

CONCLUSION

Results suggest placebo response to alcohol is associated with increased functional connectivity within a key reward network (nucleus accumbens - ventromedial prefrontal cortex and subcallosal cingulate cortex) and put forth a mechanism by which alcohol expectancies may contribute to the subjective experience of intoxication.

Intimate partner violence, substance use, and health comorbidities among women: A narrative review

Exposure to intimate partner violence (IPV), including physical, sexual, and psychological violence, aggression, and/or stalking, impacts overall health and can have lasting mental and physical health consequences. Substance misuse is common among individuals exposed to IPV, and IPV-exposed women (IPV-EW) are at-risk for transitioning from substance misuse to substance use disorder (SUD) and demonstrate greater SUD symptom severity; this too can have lasting mental and physical health consequences. Moreover, brain injury is highly prevalent in IPV-EW and is also associated with risk of substance misuse and SUD. Substance misuse, mental health diagnoses, and brain injury, which are highly comorbid, can increase risk of revictimization. Determining the interaction between these factors on the health outcomes and quality of life of IPV-EW remains a critical need. This narrative review uses a multidisciplinary perspective to foster further discussion and research in this area by examining how substance use patterns can cloud identification of and treatment for brain injury and IPV. We draw on past research and the knowledge of our multidisciplinary team of researchers to provide recommendations to facilitate access to resources and treatment strategies and highlight intervention strategies capable of addressing the varied and complex needs of IPV-EW.

Analgesic effects of alcohol in adults with chronic jaw pain

BACKGROUND

Although recent literature provides promising support for the analgesic properties of alcohol, potential differences in alcohol analgesia as a function of chronic pain status are not well understood. Thus, this study examined chronic pain status as a potential moderator of alcohol analgesia and distinguished between multiple aspects of pain experience and sensitivity: pain threshold, pain intensity, pain unpleasantness, and perceived relief.

METHODS

Social drinkers with (N = 19) and without (N = 29) chronic jaw pain completed two testing sessions in a counterbalanced order: alcohol (target BrAC = 0.08 g/dl) and placebo. In each, pressure algometry was performed at the insertion of the masseter. Alcohol analgesia was assessed by examining the main and interactive effects of beverage condition, pressure level (4, 5, or 6 pound-feet [lbf]), and chronic jaw pain status (chronic pain vs. pain-free control) on quantitative sensory testing measures and pain relief ratings following noxious stimuli.

RESULTS

Analyses indicated significant increases in pain threshold and pain relief and reductions in pain unpleasantness and pain intensity, under the alcohol condition. Chronic pain participants demonstrated lower pain thresholds and greater pain intensity and pain unpleasantness ratings than controls. There were no interactive effects of alcohol and pain conditions on any pain measure.

CONCLUSIONS

Findings provide experimental evidence of alcohol's analgesic and pain-relieving effects and suggest that these effects do not significantly differ by chronic pain status. Individuals, who self-medicate pain via alcohol consumption, irrespective of pain status, may be at increased risk to engage in hazardous drinking patterns and thus experience adverse alcohol-related consequences.

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.

Acute effects of alcohol on resting-state functional connectivity in healthy young men

Alcohol abuse and dependence remain significant public health issues, and yet the brain circuits that are involved in the rewarding effects of alcohol are poorly understood. One promising way to study the effects of alcohol on neural activity is to examine its effects on functional connectivity between brain areas involved in reward and other functions. Here, we compared the effects of two doses of alcohol (0.4 and 0.8 g/kg) to placebo on resting-state functional connectivity in brain circuits related to reward in 19 healthy young men without histories of alcohol problems. The higher, but not the lower, dose of alcohol, significantly increased connectivity from reward-related regions to sensory and motor cortex, and between seeds associated with cognitive control. Contrary to expectation, alcohol did not significantly change connectivity for the ventral striatum at either dose. These findings reveal unrecognized effects of alcohol on connectivity from reward-related regions to visual and sensory cortical areas.

Acute Alcohol Intake Produces Widespread Decreases in Cortical Resting Signal Variability in Healthy Social Drinkers

BACKGROUND

Acute alcohol intoxication has wide-ranging neurobehavioral effects on psychomotor, attentional, inhibitory, and memory-related cognitive processes. These effects are mirrored in disruption of neural metabolism, functional activation, and functional network coherence. Metrics of intraregional neural dynamics such as regional signal variability (RSV) and brain entropy (BEN) may capture unique aspects of neural functional capacity in healthy and clinical populations; however, alcohol's influence on these metrics is unclear. The present study aimed to elucidate the influence of acute alcohol intoxication on RSV and to clarify these effects with subsequent BEN analyses.

METHODS

26 healthy adults between 25 and 45 years of age (65.4% women) participated in 2 counterbalanced sessions. In one, participants consumed a beverage containing alcohol sufficient to produce a breath alcohol concentration of 0.08 g/dl. In the other, they consumed a placebo beverage. Approximately 35 minutes after beverage consumption, participants completed a 9-minute resting-state fMRI scan. Whole-brain, voxel-wise standard deviation was used to assess RSV, which was compared between sessions. Within clusters displaying alterations in RSV, sample entropy was calculated to assess BEN.

RESULTS

Compared to the placebo, alcohol intake resulted in widespread reductions in RSV in the bilateral middle frontal, right inferior frontal, right superior frontal, bilateral posterior cingulate, bilateral middle temporal, right supramarginal gyri, and bilateral inferior parietal lobule. Within these clusters, significant reductions in BEN were found in the bilateral middle frontal and right superior frontal gyri. No effects were noted in subcortical or cerebellar areas.

CONCLUSIONS

Findings indicate that alcohol intake produces diffuse reductions in RSV among structures associated with attentional processes. Within these structures, signal complexity was also reduced in a subset of frontal regions. Neurobehavioral effects of acute alcohol consumption may be partially driven by disruption of intraregional neural dynamics among regions involved in higher-order cognitive and attentional processes.