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Chronic inflammatory pain alters alcohol-regulated frontocortical signaling and associations between alcohol drinking and thermal sensitivity

ABSTRACT: Highlights • Associations between alcohol drinking and pain sensitivity change over time.• Alcohol withdrawal-induced changes in ERK phosphorylation depend on pain status.• Exposure to both alcohol and pain synchronize brain glucocorticoid signaling. Alcohol use disorder (AUD) is a chronic, relapsing psychiatric disorder that is characterized by the emergence of negative affective states. The transition from recreational, limited intake to uncontrolled, escalated intake is proposed to involve a transition from positive to negative reinforcement mechanisms for seeking alcohol. Past work has identified the emergence of significant hyperalgesia/allodynia in alcohol-dependent animals, which may serve as a key negative reinforcement mechanism. Chronic pain has been associated with enhanced extracellular signal-regulated kinase (ERK) activity in cortical and subcortical nociceptive areas. Additionally, both pain and AUD have been associated with increased activity of the glucocorticoid receptor (GR), a key mediator of stress responsiveness. The objectives of the current study were to first determine relationships between thermal nociceptive sensitivity and alcohol drinking in male Wistar rats. While inflammatory pain induced by complete Freund’s adjuvant (CFA) administration did not modify escalation of home cage drinking in animals over four weeks, the relationship between drinking levels and hyperalgesia symptoms reversed between acute (1 week) and chronic (3–4 week) periods post-CFA administration, suggesting that either the motivational or analgesic effects of alcohol may be altered over the time course of chronic pain. We next examined ERK and GR phosphorylation in pain-related brain areas (including the central amygdala and prefrontal cortex subregions) in animals experiencing acute withdrawal from binge alcohol administration (2 g/kg, 6 h withdrawal) and CFA administration (four weeks) to model the neurobiological consequences of binge alcohol exposure in the context of pain. We observed a significant interaction between alcohol and pain state, whereby alcohol withdrawal increased ERK phosphorylation across all four frontocortical areas examined, although this effect was absent in animals experiencing chronic inflammatory pain. Alcohol withdrawal also increased GR phosphorylation across all four frontocortical areas, but these changes were not altered by CFA. Interestingly, we observed significant inter-brain regional correlations in GR phosphorylation between the insula and other regions investigated only in animals exposed to both alcohol and CFA, suggesting coordinated activity in insula circuitry and glucocorticoid signaling in this context. The results of these studies provide a greater understanding of the neurobiology of AUD and will contribute to the development of effective treatment strategies for comorbid AUD and pain.

SUBMITTER: Adrienne McGinn M

PROVIDER: S-EPMC7509777 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Project description:Preclinical studies on the effects of abrupt cessation of selective serotonin reuptake inhibitors (SSRIs), a medication often prescribed in alcohol use disorder (AUD) patients with depression, results in alcohol consumption escalation after resuming drinking. However, a potential neuroinflammatory component on this escalation remains unexplored despite the immunomodulatory role of serotonin. Here, we utilized a rat model of 14-daily administration of the SSRI fluoxetine (10 mg/kg/day) along alcohol self-administration deprivation to study the effects of fluoxetine cessation on neuroinflammation after resuming alcohol drinking. Microglial morphology and inflammatory gene expression were analyzed in prelimbic cortex, striatum, basolateral amygdala and dorsal hippocampus. Results indicated that alcohol drinking reinstatement increased microglial IBA1 immunoreactivity and altered morphometric features of activated microglia (fractal dimension, lacunarity, density, roughness, and cell area, perimeter and circularity). Despite alcohol reinstatement, fluoxetine cessation modified microglial morphology in a brain region-specific manner, resulting in hyper-ramified (spatial complexity of branching), reactive (lower heterogeneity and circularity)-like microglia. We also found that microglial cell area correlated with changes in mRNA expression of chemokines (Cx3cl1/fractalkine, Cxcl12/SDF1α, Ccl2/MCP1), cytokines (IL1β, IL6, IL10) and the innate immune toll-like receptor 4 (TLR4) in dorsal hippocampus. Specifically, TLR4 correlated with microglial spatial complexity assessed by fractal dimension in striatum, suggesting a role in process branching. These findings suggest that alcohol drinking reinstatement after fluoxetine treatment cessation disturbs microglial morphology and reactive phenotype associated with a TLR4/inflammatory response to alcohol in a brain region-specific manner, facts that might contribute to alcohol-induced damage through the promotion of escalation of alcohol drinking behavior.

Project description:Alcohol consumption in the setting of chronic HCV is associated with accelerated progression towards cirrhosis, increased risk of hepatocellular carcinoma and higher mortality. This analysis contextualizes how sociodemographic factors, chronic pain and depression relate to the motivations of individuals with chronic HCV to consume alcohol. We conducted a secondary analysis of baseline data from the Hep ART trial of behavioural interventions on alcohol use among patients with HCV. Alcohol consumption was measured using the Drinking Motives Questionnaire and a novel 6-item measure of pain-related drinking motives. Statistical analyses performed included ANOVA for bivariate analyses and multivariable ordinary least-squares linear regression. At study baseline, 181 participants had an average age of 55 years; the majority (66.7%) reported beyond-minor pain; and a third (37%) met criteria for depression; drinking motives were higher for individuals with beyond-minor pain (means 9.9 vs. 4.6, p < .001) and who met criteria for depression (means 10.9 vs. 6.4, p < .001) when using the pain-related drinking motives items. Average pain(coef = 1.0410067141 < .001) was significantly associated with increased motives to drink to relieve pain in the full baseline model specification controlling for all covariates using ordinary at least squares; depression (coef = 7.06; 95% CI 1.32, 12.81; p = .016) was significantly associated with increased non-pain-related motives to drink. From baseline to 3-month follow-up, compared to participants who had mean average pain scores among the sample, motives to drink to relieve pain decreased in participants who had higher average pain scores (coef = -0.30; 95% CI -0.59, -0.01; p = .40). Physical pain and depression are associated with increased motives to consume alcohol. Patients with chronic liver disease should be screened for chronic pain and depression and, if present, referred to pain specialists or co-managed in partnership with pain specialists in hepatology clinics.

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Chronic inflammatory pain alters alcohol-regulated frontocortical signaling and associations between alcohol drinking and thermal sensitivity

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