Agmatine reduces alcohol drinking and produces antinociceptive effects in rodent models of alcohol use disorder

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.

KCa2 channel positive modulation reduces alcohol drinking in female C57BL/6J mice

Although men have historically exhibited higher levels of alcohol use disorder (AUD) diagnosis, the gap between men and women has been diminishing quickly. Preclinical screening for pharmacological treatments for AUD has typically focused solely on males, ignoring the possibility that males and females may differ mechanistically for the same behavioral phenotype. To ensure the efficacy of treatment targets across the sexes, it is crucial to study the pharmacological effects of AUD treatments in males and females. While positive KCa2 channel modulation can reduce ethanol consumption and seeking behaviors, withdrawal-induced hyperexcitability, and negative affective behaviors in male rodents, the effect of KCa2 channel modulation on female ethanol consumption has not been reported. To determine the efficacy of KCa2 channel positive modulation in female C57BL/6J mice, we assessed the ability of the KCa2 channel positive modulator 1-EBIO to affect locomotor activity, voluntary home cage ethanol intake prior to and following chronic intermittent ethanol (CIE) exposure, and voluntary home cage sucrose drinking. There were no significant changes to distance traveled in an open field apparatus following administration of 1-EBIO in our locomotor assay. In ethanol drinking mice, 1-EBIO significantly reduced ethanol consumption in air controls and CIE exposed mice, without altering water consumption. While administration of 1-EBIO did not affect consumption of sucrose in male mice, 1-EBIO significantly increased sucrose intake in females. Together, these data provide further evidence that KCa2 channel positive modulation is a promising therapeutic target to reduce ethanol drinking in males and females alike.

Chronic intermittent ethanol produces nociception through endocannabinoid-independent mechanisms in mice

Alcohol use disorder (AUD) affects millions of people and represents a significant health and economic burden. Pain represents a frequently under-treated aspect of hyperkatifeia during alcohol withdrawal, yet to date no drugs have received FDA approval for the treatment of this indication in AUD patients. This study aims to evaluate the potential of targeting bioactive lipid signaling pathways as a therapeutic approach for treating alcohol withdrawal-related pain. We utilized a chronic intermittent ethanol (CIE) vapor exposure model in C57BL/6J mice of both sexes to establish alcohol dependence, and demonstrated that CIE mice developed robust tactile allodynia and thermal hyperalgesia during withdrawal that was independent of prior blood alcohol levels. Next, we evaluated four drugs for their efficacy in reversing tactile allodynia during abstinence from CIE using a cross-over treatment design that included FDA-approved naltrexone as well as commercially available inhibitors targeting inflammatory lipid signaling enzymes including fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and 15-Lipoxygenase (LOX). None of these compounds produced significant therapeutic benefit in reversing established CIE-induced tactile allodynia, despite attenuating pain-like behaviors at these doses in other chronic pain models. Additionally, we assessed plasma endocannabinoid levels in both sexes during withdrawal. We found that there is an inherent sex difference in the endogenous anti-inflammatory endocannabinoid tone in naive mice and CIE treatment affected endocannabinoids levels in female mice only. These findings underscore the need to better understand the driving causes of AUD induced pain and to develop novel therapeutic approaches to mitigate pain in AUD patients.

Animal models for studying therapeutic targets and treatments for alcohol use disorder

Over the decades, preclinical models have been developed and refined to investigate the rewarding effects of addictive substances and the neurobiological underpinnings of alcohol and other drug use disorders. This chapter delves into the methodological foundations, advantages, and limitations of leading animal models used to study alcohol use disorders (AUDs). Some models focus on the early stages of alcohol use and abuse. For instance, conditioned place preference assesses associative learning between a specific context and the effects of the drug, while locomotor sensitization measures increased locomotor activity following repeated drug exposure. In contrast, contingent models such as operant and non-operant alcohol self-administration protocols gauge voluntary intake, preference, motivation, and seeking behavior for alcohol solutions among experimental subjects. Additionally, we discuss the chronic intermittent alcohol vapor model, extensively utilized to induce a phenotype resembling dependence through non-contingent inhalation of alcohol vapor, resulting in elevated blood alcohol concentrations. Given the focus on pharmacological treatments for AUDs, we explore how different animal models can be employed to evaluate potential therapies and extrapolate findings to alcohol-related behaviors in humans. This chapter aims to provide readers with a comprehensive understanding of various animal models for AUDs, aiding in the interpretation of preclinical studies and the selection of suitable models for future research endeavors.

Histone deacetylase inhibitor decreases hyperalgesia in a mouse model of alcohol withdrawal-induced hyperalgesia

BACKGROUND

Alcohol withdrawal-induced hyperalgesia (AWH) is characterized as an increased pain sensitivity observed after cessation of chronic alcohol use. Alcohol withdrawal-induced hyperalgesia can contribute to the negative affective state associated with abstinence and can increase susceptibility to relapse. We aimed to characterize pain sensitivity in mice during withdrawal from two different models of alcohol exposure: chronic drinking in the dark (DID) and the Lieber-DeCarli liquid diet. We also investigated whether treatment with a histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), could ameliorate AWH in mice treated with the Lieber-DeCarli diet.

METHODS

Male and female C57BL/6J mice were used for these studies. In the DID model, mice received bottles of 20% ethanol or water during the dark cycle for 4 h per day on four consecutive days per week for 6 weeks. Peripheral mechanical sensitivity was measured weekly the morning of Day 5 using von Frey filaments. In the Lieber-DeCarli model, mice received ethanol (5% v/v) or control liquid diet for 10 days, along with a single binge ethanol gavage (5 g/kg) or control gavage, respectively, on Day 10. Peripheral mechanical sensitivity was measured during the liquid diet administration and at 24 and 72 h into ethanol withdrawal. An independent group of mice that received the Lieber-DeCarli diet were administered SAHA (50 mg/kg, i.p.) during withdrawal.

RESULTS

Male mice exhibited mechanical hypersensitivity after consuming ethanol for 5 weeks in the DID procedure. In the Lieber-DeCarli model, ethanol withdrawal led to hyperalgesia in both sexes. Suberoylanilide hydroxamic acid treatment during withdrawal from the ethanol liquid diet alleviated AWH.

CONCLUSIONS

These results demonstrate AWH in mice after chronic binge drinking in males and after Lieber-DeCarli liquid diet administration in both sexes. Like previous findings in rats, HDAC inhibition reduced AWH in mice, suggesting that epigenetic mechanisms are involved in AWH.

Preventive putative effect of agmatine on cognitive and molecular outcomes in ventral tegmental area of male offspring following physical and psychological prenatal stress

Prenatal stress (PS) results from a maternal experience of stressful events during pregnancy, which has been associated with an increased risk of behavioral disorders including substance abuse and anxiety in the offspring. PS is known to result in heightened dopamine release in the ventral tegmental area (VTA), in part through the effects of corticotropin-releasing hormone, which directly excites dopaminergic cells. It has recently been suggested that agmatine plays a role in modulating anxiety-like behaviors. In this study, we investigated whether agmatine could reduce negative cognitive outcomes in male mice prenatally exposed to psychological/physical stress, and whether this could be associated with molecular changes in VTA. Agmatine (37.5 mg/kg) was administrated 30 min prior to PS induction in pregnant Swiss mice. Male offspring were evaluated in a series of behavioral and molecular assays. Findings demonstrated that agmatine reduced the impairment in locomotor activity induced by both psychological and physical PS. Agmatine also decreased heightened conditioned place preference to morphine seen in PS offspring. Moreover, agmatine ameliorated the anxiety-like behavior and drug-seeking behavior induced by PS in the male offspring. Molecular effects were seen in VTA as the enhanced brain-derived neurotrophic factor (BDNF) induced by PS in the VTA was reduced by agmatine. Behavioral tests indicate that agmatine exerts a protective effect on PS-induced impairments in male offspring, which could be due in part to agmatine-associated molecular alterations in the VTA. Taken together, our data suggest that prenatal treatment with agmatine exerts protective effect against negative consequences of PS on the development of affective circuits in the offspring.