Hyperalgesia after a Drinking Episode in Young Adult Binge Drinkers: A Cross-Sectional Study

Alcohol and cannabis use for pain management: Translational findings of relative risks, benefits, and interactions

Chronic pain affects over 20% of the global population and contributes to the vast burden of psychiatric illness. While effective treatments for chronic pain remain limited, both alcohol and cannabis have been used for centuries to manage pain and closely associated negative affective symptoms. However, persistent misuse of alcohol and/or cannabis in such a negative reinforcement fashion is hypothesized to increase the risk of severity of substance use disorders (SUDs). The current review describes neurobiological evidence for the analgesic efficacy of alcohol and primary cannabis constituents and how use or co-use of these substances may influence SUD risk.

Adolescent alcohol exposure promotes mechanical allodynia and alters synaptic function at inputs from the basolateral amygdala to the prelimbic cortex

Binge drinking is common among adolescents despite mounting evidence linking it to various adverse health outcomes that include heightened pain perception. The prelimbic (PrL) cortex is vulnerable to insult from adolescent alcohol exposure and receives input from the basolateral amygdala (BLA) while sending projections to the ventrolateral periaqueductal gray (vlPAG) - two brain regions implicated in nociception. In this study, adolescent intermittent ethanol (AIE) exposure was carried out in male and female rats using a vapor inhalation procedure. Assessments of mechanical and thermal sensitivity revealed that AIE exposure-induced protracted mechanical allodynia. To investigate synaptic function at BLA inputs onto defined populations of PrL neurons, retrobeads and viral labeling were combined with optogenetics and slice electrophysiology. Recordings from retrobead labeled cells in the PrL revealed AIE reduced BLA-driven feedforward inhibition of neurons projecting from the PrL to the vlPAG, resulting in augmented excitation/inhibition (E/I) balance and increased intrinsic excitability. Consistent with this finding, recordings from virally tagged PrL parvalbumin interneurons (PVINs) demonstrated that AIE exposure reduced both E/I balance at BLA inputs onto PVINs and PVIN intrinsic excitability. These findings provide compelling evidence that AIE alters synaptic function and intrinsic excitability within a prefrontal nociceptive circuit.

Treating chronic stress and chronic pain by manipulating gut microbiota with diet: can we kill two birds with one stone?

Background: Chronic stress and chronic pain are closely linked by the capacity to exacerbate each other, sharing common roots in the brain and in the gut. The strict intersection between these two neurological diseases makes important to have a therapeutic strategy aimed at preventing both to maintain mental health in patients. Diet is an modifiable lifestyle factor associated with gut-brain axis diseases and there is growing interest in its use as adjuvant to main therapies. Several evidence attest the impact of specific diets or nutrients on chronic stress-related disorders and pain with a good degree of certainty. A daily adequate intake of foods containing micronutrients such as amino acids, minerals and vitamins, as well as the reduction in the consumption of processed food products can have a positive impact on microbiota and gut health. Many nutrients are endowed of prebiotic, anti-inflammatory, immunomodulatory and neuroprotective potential which make them useful tools helping the management of chronic stress and pain in patients. Dietary regimes, as intermittent fasting or caloric restriction, are promising, although further studies are needed to optimize protocols according to patient's medical history, age and sex. Moreover, by supporting gut microbiota health with diet is possible to attenuate comorbidities such as obesity, gastrointestinal dysfunction and mood disorders, thus reducing healthcare costs related to chronic stress or pain.Objective: This review summarize the most recent evidence on the microbiota-mediated beneficial effects of macro- and micronutrients, dietary-related factors, specific nutritional regimens and dietary intervention on these pathological conditions.

Adolescent alcohol exposure promotes mechanical allodynia and alters synaptic function at inputs from the basolateral amygdala to the prelimbic cortex

Binge drinking is common among adolescents despite mounting evidence linking it to various adverse health outcomes that include heightened pain perception. The prelimbic (PrL) cortex is vulnerable to insult from adolescent alcohol exposure and receives input from the basolateral amygdala (BLA) while sending projections to the ventrolateral periaqueductal gray (vlPAG) - two brain regions implicated in nociception. In this study, adolescent intermittent ethanol (AIE) exposure was carried out in male and female rats using a vapor inhalation procedure. Assessments of mechanical and thermal sensitivity revealed that AIE exposure induced protracted mechanical allodynia. To investigate synaptic function at BLA inputs onto defined populations of PrL neurons, retrobeads and viral labelling were combined with optogenetics and slice electrophysiology. Recordings from retrobead labelled cells in the PrL revealed AIE reduced BLA driven feedforward inhibition of neurons projecting from the PrL to the vlPAG, resulting in augmented excitation/inhibition (E/I) balance and increased intrinsic excitability. Consistent with this finding, recordings from virally tagged PrL parvalbumin interneurons (PVINs) demonstrated that AIE exposure reduced both E/I balance at BLA inputs onto PVINs and PVIN intrinsic excitability. These findings provide compelling evidence that AIE alters synaptic function and intrinsic excitability within a prefrontal nociceptive circuit.

Alcohol consumption after downhill running does not affect muscle recovery but prolongs pain perception in East Asian men

PURPOSE

Alcoholic beverages are commonly consumed following athletic competitions and strenuous exercise for celebration or relaxation purposes. Whether and how alcohol consumption influences muscle recovery and perceived pain following unaccustomed eccentric exercise is unclear. We aimed to determine the effects of alcohol consumption after downhill running on muscular strength and perceived pain in East Asian men.

METHODS

Twenty-four young men performed 45 min of downhill (-10%) running at a corresponding speed of 70% VO2 max. Immediately after downhill running and again 24 h later, the participants consumed either an alcoholic beverage (1 g ethanol/kg body weight, alcohol group, n=12) or the same quantity of water (control group, n=12).

RESULTS

Peak isometric and concentric muscle contraction torques during knee extension (via the isokinetic dynamometer) and squat jump height decreased 24 h after downhill running (all p<0.05); however, there were no significant differences between the two groups. The visual analog scores for pain (pain scores) in the quadriceps, hamstring, gastrocnemius, and gluteus maximus muscles increased at 24 h and 48 h in both groups (all p<0.05). Pain scores in the quadriceps decreased gradually from 24 h to 48 h in the control group, but no such trend was observed in the alcohol group (group × time interaction effect; F=4.47, p<0.05).

CONCLUSION

Acute alcohol consumption does not seem to affect muscle strength or jump performance during recovery. However, the effects on pain appear to persist longer after alcohol consumption in East Asian men.

Preoperative Alcohol Use, Postoperative Pain, and Opioid Use After Coronary Artery Bypass Surgery

OBJECTIVES

Chronic alcohol use is associated with chronic pain and increased opioid consumption. The association between chronic alcohol use and acute postoperative pain has been studied minimally. The authors' objective was to explore the association among preoperative alcohol use, postoperative pain, and opioid consumption after coronary artery bypass grafting (CABG).

DESIGN

A retrospective cohort study.

SETTING

At a single academic medical center.

PARTICIPANTS

Patients having isolated CABG.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographics, comorbidities, and baseline alcohol consumption were recorded. Primary outcomes were mean pain score and morphine milligram equivalent (MME) consumption on postoperative day 0. Among 1,338 patients, there were 764 (57.1%) who had no weekly preoperative alcohol use, 294 (22.0%) who drank ≤1 drink per week, 170 (12.7%) who drank 2-to-7 drinks per week, and 110 (8.2%) who drank 8 or more drinks per week. There was no significant difference in mean pain score on postoperative day 0 in patients who consumed different amounts of alcohol (no alcohol = 5.3 ± 2.2, ≤1 drink = 5.2 ± 2.1, 2 to 7 drinks = 5.3 ± 2.3, 8 or more drinks = 5.4 ± 1.9, p = 0.66). There was also no significant difference in median MME use on postoperative day 0 in patients who consumed different amounts of alcohol (no alcohol = 22.5 mg, ≤1 drink = 21.1 mg, 2-to-7 drinks = 24.8 mg, 8 or more drinks = 24.5 mg, p = 0.14).

CONCLUSIONS

There is no apparent association among mild-to-moderate preoperative alcohol consumption and early postoperative pain and opioid use in patients who underwent CABG.

Alcohol use and the pain system

The World Health Organization's epidemiological data from 2016 revealed that while 57% of the global population aged 15 years or older had abstained from drinking alcohol in the previous year, more than half of the population in the Americas, Europe, and Western Pacific consumed alcohol. The spectrum of alcohol use behavior is broad: low-risk use (sensible and in moderation), at-risk use (e.g., binge drinking), harmful use (misuse) and dependence (alcoholism; addiction; alcohol use disorder). The at-risk use and misuse of alcohol is associated with the transition to dependence, as well as many damaging health outcomes and preventable causes of premature death. Recent conceptualizations of alcohol dependence posit that the subjective experience of pain may be a significant contributing factor in the transition across the spectrum of alcohol use behavior. This narrative review summarizes the effects of alcohol at all levels of the pain system. The pain system includes nociceptors as sensory indicators of potentially dangerous stimuli and tissue damage (nociception), spinal circuits mediating defensive reflexes, and most importantly, the supraspinal circuits mediating nocifensive behaviors and the perception of pain. Although the functional importance of pain is to protect from injury and further or future damage, chronic pain may emerge despite the recovery from, and absence of, biological damage (i.e., in the absence of nociception). Like other biological perceptual systems, pain is a construction contingent on sensory information and a history of individual experiences (i.e., learning and memory). Neuroadaptations and brain plasticity underlying learning and memory and other basic physiological functions can also result in pathological conditions such as chronic pain and addiction. Moreover, the negative affective/emotional aspect of pain perception provides embodied and motivational components that may play a substantial role in the transition from alcohol use to dependence.

Long-lasting mechanical hypersensitivity and CRF receptor type-1 neuron activation in the BNST following adolescent ethanol exposure

BACKGROUND

Adolescent alcohol use can produce long-lasting alterations in brain function, potentially leading to adverse health outcomes in adulthood. Emerging evidence suggests that chronic alcohol use can increase pain sensitivity or exacerbate existing pain conditions, but the potential neural mechanisms underlying these effects require further investigation. Here, we evaluate the impact of chronic ethanol vapor on mechanical sensitivity over the course of acute and protracted withdrawal in adolescent and adult male and female mice, and its potential association with alterations in corticotropin-releasing factor (CRF) signaling within the bed nucleus of the stria terminalis (BNST).

METHODS

Adolescent and adult male and female mice underwent intermittent ethanol vapor exposure on 4 days/week for 2 weeks. Mechanical thresholds were evaluated 5 h and 7, 14, 21, and 28 d after cessation of ethanol exposure using the von Frey test. For mice with a history of adolescent ethanol exposure, brains were collected for in situ RNAscope processing after the final test. Messenger RNA expression of c-Fos, Crfr1, and Crf in the BNST subregions was examined.

RESULTS

Exposure to intermittent ethanol vapor induced persistent mechanical hypersensitivity during withdrawal in both adolescent and adult mice. Notably, the effect was more transient in mice exposed to ethanol during adulthood, resolving by day 28 after ethanol exposure. Furthermore, both male and female mice with a history of adolescent ethanol exposure exhibited increased activation of CRF receptor type 1 (CRFR1) neurons within the dorsolateral BNST.

CONCLUSIONS

Our results support the conclusion that intermittent ethanol exposure can induce mechanical hypersensitivity, potentially through the activation of BNST CRFR1 neurons. These findings provide a basis for future studies aimed at evaluating specific subpopulations of BNST neurons and their contribution to pain in individuals with a history of alcohol use.

Elevated creatinine kinase levels amongst Dutch adolescents with acute alcohol intoxication

This study aims to explore the prevalence of creatinine kinase elevation amongst a sample of Dutch adolescents admitted for acute alcohol intoxication. The data on all admitted adolescents < 18 years old with acute alcohol intoxication between 2008 and 2021 were collected from a Dutch major district general hospital, Reinier de Graaf Gasthuis, in Delft. Overall, 495 adolescents who were treated for symptoms of acute alcohol intoxication during this period were included in the study. When evaluating the blood samples of the included patients, elevated creatinine kinase levels were found in 60% of the cases, with a mean of 254 U/I (normal value ≤ 145 U/I). A confirmed diagnosis of rhabdomyolysis (increase in CK > fivefold the upper limit of normal) was present in 4.4% of cases. Moreover, using a linear regression this study found that a higher blood alcohol concentration was associated with higher creatinine kinase levels, when adjusted for positive drug screenings amongst the adolescents with acute alcohol intoxication (p = 0.027; β = 66.88; 95% CI 7.68 - 126.08).    Conclusions: This is the first study focusing on how acute alcohol intoxication affects adolescents' muscle tissue. The results could potentially help to prevent alcohol use within the sports world. It could also aid understanding of how acute alcohol intoxication influences the breakdown of adolescents' muscle tissue. What is Known: • Alcohol, alongside pharmaceutical agents and illicit drugs, is a significant cause of rhabdomyolysis (increase in creatinine kinase > fivefold the upper limit of normal). • Creatinine kinase elevation in alcohol intoxicated patients may be as a result of direct "muscular" toxicity" (myotoxicity) or from prolonged immobilization and ischemic compression induced by coma. What is New: • Our retrospective cohort study is a pioneer in addressing the effect of acute alcohol intoxication amongst adolescents (< 18 years) upon muscle tissue (creatinine kinase level) within a large population. When evaluating the blood samples of the included population, elevated creatinine kinase levels were found in 60% of the cases, with a mean of 254 U/I (normal value ≤ 145 U/I). • There is an association between alcohol intoxication and elevated creatinine kinase levels amongst adolescents. Future research is needed to further understand the pathophysiology and causality of this interaction.

HPA-Axis Activity and Nutritional Status Correlation in Individuals with Alcohol Use Disorder

Impaired activity of the hypothalamic-pituitary-adrenal axis (HPA-axis) is evident in alcohol use disorder (AUD), and may be implicated in various nutritional and metabolic alterations often seen in individuals with this disorder. The present study examined a possible correlation between HPA-axis activity and nutritional status components in individuals with AUD. Fourteen AUD and fourteen non-AUD males participated; anthropometric and body composition measurements were made, and fasting blood samples were analysed for plasma adrenal corticotropic hormone (ACTH), catecholamines, cortisol and beta-endorphin. Nutrient intake was estimated via a three-day diet record. Waist circumference and waist-to-hip ratio were increased in the AUD group. Thiamine and folic intake were lower in AUD group, although only folic acid intake was insufficient in both AUD and non-AUD groups. Increased epinephrine and norepinephrine were also observed in AUD group compared to non-AUD group. No clear correlation between HPA-axis activity and nutritional status components was found. This study showed that nutrient intake, body composition, and HPA-axis activity were different among AUD and non-AUD individuals. More research on the correlation between nutritional status and HPA-axis activity in AUD individuals should be conducted.

2-Arachidonoylglycerol-mediated endocannabinoid signaling modulates mechanical hypersensitivity associated with alcohol withdrawal in mice

BACKGROUND

Alcohol use disorder (AUD) commonly occurs in patients with chronic pain, and a major barrier to achieving abstinence and preventing relapse is the emergence of hyperalgesia during alcohol withdrawal. Elucidating novel therapeutic approaches to target hyperalgesia associated with alcohol withdrawal could have important implications for treating AUD. Here, we examined the role of 2-arachidonoylglycerol (2-AG)-mediated endocannabinoid (eCB) signaling in the regulation of hyperalgesia associated with alcohol withdrawal in mice. We tested the hypothesis that pharmacological augmentation of 2-AG signaling could reduce hyperalgesia during withdrawal.

METHODS

Male and female C57BL/6J mice were tested during withdrawal from a continuous access two-bottle choice (2BC) paradigm to investigate how eCB signaling modulates mechanical and thermal sensitivity during withdrawal. Mice were pretreated with the monoacylglycerol lipase (MAGL) inhibitor JZL184 to elevate levels of 2-AG. Rimonabant or AM630 were given to block CB1 and CB2 receptor activity, respectively. DO34 was given to reduce 2-AG by inhibiting the 2-AG synthetic enzyme diacylglycerol lipase (DAGL).

RESULTS

After 72 h of withdrawal, male and female mice exhibited increased mechanical, but not thermal, hypersensitivity, which normalized by 7 days. This effect was reversed by pretreatment with JZL184. The effects of JZL184 were prevented by coadministration of either the CB1 or the CB2 antagonist. DO34, Rimonabant, and AM630 exacerbated mechanical hypersensitivity during alcohol withdrawal, causing an earlier onset and persistent hypersensitivity even 1 week into withdrawal.

CONCLUSIONS

Our findings demonstrate the critical role of 2-AG signaling in the bidirectional regulation of mechanical sensitivity during alcohol withdrawal, with enhancement of 2-AG levels reducing sensitivity, and inhibition of 2-AG signaling exacerbating sensitivity. These data suggest that 2-AG augmentation represents a novel approach to the treatment of alcohol withdrawal-associated hyperalgesia and AUD in patients with comorbid pain disorders.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

Differences in the association between kappa opioid receptors and pain among Black and White adults with alcohol use disorders

BACKGROUND

The relationship between alcohol and pain is complex. Associations between pain and alcohol use disorder (AUD) vary by race, but the underlying biological basis is not understood. We examined the association of the kappa opioid receptor (KOR) with responses to the cold-pressor test (CPT), before and after treatment with the opioid antagonist naltrexone, among individuals with AUD who self-identified as Black or White.

METHODS

Thirty-seven individuals (12 Black, 24 White, and 1 Multiracial) with AUD participated in two CPTs, separated by 1 week during which they received naltrexone 100 mg daily. During each CPT, pain reporting threshold (PRT), average pain increase rate (APIR), relative pain recovery (RPR), and alcohol craving were recorded. KOR availability was measured using [¹¹ C]-LY2795050 positron emission tomography (PET) prior to treatment with naltrexone.

RESULTS

Black participants reported higher PRT and APIR than White participants during the CPT before, but not after, naltrexone treatment. Among Black participants, KOR availability was positively associated with PRT and APIR before, but not after naltrexone. Greater KOR availability was associated with faster RPR for White, but not Black, participants. The CPT induced more alcohol craving in Black than White participants, particularly in individuals with low KOR availability, an effect that was not attenuated by naltrexone.

CONCLUSIONS

KOR involvement and naltrexone effects on responses to the CPT were different between Black and White participants. These preliminary findings suggest that further exploration of the differences in the opioid system and pain among Black and White individuals with AUD and their relationship with naltrexone's effects is warranted.

Probiotics attenuate alcohol-induced muscle mechanical hyperalgesia: Preliminary observations

Alcohol use disorder (AUD) is a major health problem that causes millions of deaths annually world-wide. AUD is considered to be a chronic pain disorder, that is exacerbated by alcohol withdrawal, contributing to a high (∼80%) relapse rate. Chronic alcohol consumption has a marked impact on the gut microbiome, recognized to have a significant effect on chronic pain. We tested the hypothesis that modulating gut microbiota through feeding rats with probiotics can attenuate alcohol-induced muscle mechanical hyperalgesia. To test this hypothesis, rats were fed alcohol (6.5%, 4 days on 3 days off) for 3 weeks, which induced skeletal muscle mechanical hyperalgesia. Following alcohol feeding, at which time nociceptive thresholds were ∼37% below pre-alcohol levels, rats received probiotics in their drinking water, either Lactobacillus Rhamnosus GG (Culturelle) or De Simone Formulation (a mixture of 8 bacterial species) for 8 days; control rats received plain water to drink. When muscle mechanical nociceptive threshold was evaluated 1 day after beginning probiotic feeding, nociceptive thresholds were significantly higher than rats not receiving probiotics. Mechanical nociceptive thresholds continued to increase during probiotic feeding, with thresholds approaching pre-alcohol levels 5 days after starting probiotics; nociceptive threshold in rats not receiving probiotics remained low. After probiotics were removed from the drinking water, nociceptive thresholds gradually decreased in these two groups, although they remained higher than the group not treated with probiotic (21 days after ending alcohol feeding). These observations suggest that modification of gut microbiota through probiotic feeding has a marked effect on chronic alcohol-induced muscle mechanical hyperalgesia. Our results suggest that administration of probiotics to individuals with AUD may reduce pain associated with alcohol consumption and withdrawal, and may be a novel therapeutic intervention to reduce the high rate of relapse seen in individuals with AUD attempting to abstain from alcohol.

Elevated customary alcohol consumption attenuates opioid effects

BACKGROUND

Regular alcohol consumption is on the rise among older adults and has the potential of altering the subjective experience of pain and response to pain medications. This study examined the cognitive, analgesic and side effect response to oxycodone in middle age and older adults with elevated levels of customary alcohol consumption in a human laboratory setting.

METHODS

After refraining from alcohol for one day, eligible participants underwent baseline assessment cognition and side effects by means of questionnaires that were repeated at three time points (90 min, 5 and 8 h) following administration of a 10 mg oral dose of oxycodone. Response to pain stimulus (Cold Pressor Test (CPT)), pupil size, and plasma oxycodone were also measured.

RESULTS

One hundred twenty-eight adults (age 35-85) completed the study day. Compared to those with lower customary alcohol consumption, participants with elevated alcohol consumption showed attenuated opioid-induced pupil constriction and cognitive decline on objective measures of working memory, sustained attention, inhibitory control, coordination on a simulated driving task, and subjective dysphoric effects with enhanced subjective euphoric effects. Oxycodone pharmacokinetics, pain tolerance to CPT, and Berg balance were impacted comparably between alcohol consumption groups. Women endorsed greater negative drug effects, whereas men endorsed positive drug effects.

CONCLUSION

Independent of subject's age, elevated customary alcohol consumption attenuates opioid central effects (i.e., pupil miosis, impaired cognition) and gender influences subjective drug effects. Clinicians should consider alcohol consumption and gender when prescribing opioid medications.

The Role of Melanocortin Plasticity in Pain-Related Outcomes After Alcohol Exposure

The global COVID-19 pandemic has shone a light on the rates and dangers of alcohol misuse in adults and adolescents in the US and globally. Alcohol exposure during adolescence causes persistent molecular, cellular, and behavioral changes that increase the risk of alcohol use disorder (AUD) into adulthood. It is established that alcohol abuse in adulthood increases the likelihood of pain hypersensitivity and the genesis of chronic pain, and humans report drinking alcohol to relieve pain symptoms. However, the longitudinal effects of alcohol exposure on pain and the underlying CNS signaling that mediates it are understudied. Specific brain regions mediate pain effects, alcohol effects, and pain-alcohol interactions, and neural signaling in those brain regions is modulated by neuropeptides. The CNS melanocortin system is sensitive to alcohol and modulates pain sensitivity, but this system is understudied in the context of pain-alcohol interactions. In this review, we focus on the role of melanocortin signaling in brain regions sensitive to alcohol and pain, in particular the amygdala. We also discuss interactions of melanocortins with other peptide systems, including the opioid system, as potential mediators of pain-alcohol interactions. Therapeutic strategies that target the melanocortin system may mitigate the negative consequences of alcohol misuse during adolescence and/or adulthood, including effects on pain-related outcomes.