Effect of ketamine on binge drinking patterns in crossed high alcohol-preferring (cHAP) mice

Dorsomedial striatal AMPA receptor antagonism increases alcohol binge drinking in selectively bred crossed high alcohol preferring mice

Crossed high alcohol preferring (cHAP) mice have been selectively bred to consume considerable amounts of alcohol resulting in binge drinking. The dorsomedial striatum (DMS) is a brain region involved in goal-directed action selection, and dorsolateral striatum (DLS) is a brain region involved in habitual action selection. Alcohol use disorder (AUD) may involve a disruption in the balance between the DMS and DLS. While the DLS is involved in binge drinking, the reliance on the DMS and DLS in binge drinking has not been investigated in cHAP mice. We have previously demonstrated that glutamatergic activity in the DLS is necessary for binge-like alcohol drinking in C57BL/6J mice, another high drinking mouse. Because of this, we hypothesised that DLS glutamatergic activity would gate binge-like alcohol drinking in cHAP mice. cHAP mice underwent bilateral cannulation into the DMS or DLS and were allowed free-access to 20% alcohol for 2 h each day for 11 days. Mice were microinjected with the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antagonist, NBQX, into the DMS or DLS immediately prior to alcohol access. AMPAR protein expression was also assessed in a separate group of animals in the DMS and DLS following an 11-day drinking history. We found that intra-DMS (but not intra-DLS) NBQX alters binge alcohol drinking, with intra-DMS NBQX increasing alcohol consumption. We also found that the ratio of GluA1 to GluA2 differs across dorsal striatal subregions. Together, these findings suggest that glutamatergic activity in the DMS may serve to limit binge drinking in cHAP mice.

Home cage voluntary alcohol consumption increases binge drinking without affecting abstinence-related depressive-like behaviors or operant responding in crossed high alcohol-preferring mice (cHAPs)

Chronic alcohol consumption can lead to tolerance and escalation of drinking in humans and animals, but mechanisms underlying these changes are not fully characterized. Preclinical models can delineate which mechanisms are involved. The chronic intermittent ethanol exposure (CIE) procedure uses forced exposure to vaporized alcohol that elicits withdrawal and increased responding for alcohol in operant tasks in C57BL/6J inbred mice. Chronic two-bottle choice (2BC) drinking in the same strain elicits abstinent-related depression-like behavior, suggestive of allostatic changes. Selected lines such as crossed High Alcohol Preferring (cHAP) mice voluntarily drink to blood alcohol concentrations comparable to those attained in CIE and could be used to assess how alcohol affects these same endpoints without the confounds of involuntary vapor inhalation. In three experiments, we assess how 2BC drinking in cHAP mice affects abstinence-related depressive- and anxiety-like behavior, operant responding for alcohol, and binge consumption using drinking-in-the-dark (DID). We hypothesized that cHAPs with home-cage drinking experience would exhibit more depressive behavior after abstinence, increased responding for alcohol in the operant box, and increased DID intake. Of these, a drinking history increased DID intake in female cHAPs only and increased sucrose preference and intake following abstinence, but had no effects on operant responding or NSFT latency and FST immobility following forced abstinence. These results are consistent with recent findings using slice electrophysiology showing tolerance to alcohol's actions on the dorsolateral striatum following 2BC drinking in female, but not male cHAP mice. Overall, these data suggest that cHAPs may require procedures allowing rapid intoxication, such as DID, to demonstrate changes in alcohol's rewarding effects.

Epigenetic drugs and psychedelics as emerging therapies for alcohol use disorder: insights from preclinical studies

Alcohol use disorder (AUD) is a public health issue that affects millions of people worldwide leading to physical, mental and socio-economic consequences. While current treatments for AUD have provided relief to individuals, their effectiveness on the long term is often limited, leaving a number of affected individuals without sustainable solutions. In this review, we aim to explore two emerging approaches for AUD: psychedelics and epigenetic drugs (i.e., epidrugs). By examining preclinical studies, different animal species and procedures, we delve into the potential benefits of each of these treatments in terms of addictive behaviors (alcohol drinking and seeking, motivation to drink alcohol and prevention of relapse). Because psychedelics and epidrugs may share common and complementary mechanisms of action, there is an exciting opportunity for exploring synergies between these approaches and their parallel effectiveness in treating AUD and the diverse associated psychiatric conditions.

Non-consummatory behavior signals predict aversion-resistant alcohol drinking in head-fixed mice

A key facet of alcohol use disorder is continuing to drink alcohol despite negative consequences (so called "aversion-resistant drinking"). In this study, we sought to assess the degree to which head-fixed mice exhibit aversion-resistant drinking and to leverage behavioral analysis techniques available in head-fixture to relate non-consummatory behaviors to aversion-resistant drinking. We assessed aversion-resistant drinking in head-fixed female and male C57BL/6 J mice. We adulterated 20% (v/v) alcohol with varying concentrations of the bitter tastant quinine to measure the degree to which mice would continue to drink despite this aversive stimulus. We recorded high-resolution video of the mice during head-fixed drinking, tracked body parts with machine vision tools, and analyzed body movements in relation to consumption. Female and male head-fixed mice exhibited heterogenous levels of aversion-resistant drinking. Additionally, non-consummatory behaviors, such as paw movement and snout movement, were related to the intensity of aversion-resistant drinking. These studies demonstrate that head-fixed mice exhibit aversion-resistant drinking and that non-consummatory behaviors can be used to assess perceived aversiveness in this paradigm. Furthermore, these studies lay the groundwork for future experiments that will utilize advanced electrophysiological techniques to record from large populations of neurons during aversion-resistant drinking to understand the neurocomputational processes that drive this clinically relevant behavior. This article is part of the Special Issue on "PFC circuit function in psychiatric disease and relevant models".

[Interest and mechanisms of action of ketamine in alcohol addiction- A review of clinical and preclinical studies]

Alcohol Use Disorder (AUD) is a psychiatric condition characterized by chronic and excessive drinking despite negative consequences on overall health and social or occupational functioning. There are currently limited treatment options available for AUD, and the effects size and the response rates to these treatments are often low to moderate. The World Health Organization has identified the development of medications to treat AUD as one of its 24 priorities. This past decade was marked by a renewed interest in psychedelic use in psychiatry. At the centre of this renaissance, ketamine, an atypical psychedelic already used in the treatment of major depression, is an NMDA receptor antagonist that exists as a racemic compound made of two enantiomers, S-ketamine, and R-ketamine. Each form can be metabolized into different metabolites, some of which having antidepressant properties. In this article, we review both clinical and preclinical studies on ketamine and its metabolites in the treatment of AUD. Preclinical as well as clinical studies have revealed that ketamine is effective in reducing withdrawal symptoms and alcohol craving. Convergent data showed that antidepressant properties of ketamine largely contribute to the decreased likelihood of alcohol relapse, especially in patients undergoing ketamine-assisted psychotherapies. Its effectiveness is believed to be linked with its ability to regulate the glutamatergic pathway, enhance neuroplasticity, rewire brain resting state network functional connectivity and decrease depressive-like states. However, it remains to further investigate (i) why strong differences exist between male and female responses in preclinical studies and (ii) the respective roles of each of the metabolites in the ketamine effects in both genders. Interestingly, current studies are also focusing on ketamine addiction and the comorbidity between alcohol addiction and depression occurring more frequently in females.

Non-Consummatory Behavior Signals Predict Aversion-Resistant Alcohol Drinking in Head-Fixed Mice

A key facet of alcohol use disorder is continuing to drink alcohol despite negative consequences (so called "aversion-resistant drinking"). In this study, we sought to assess the degree to which head-fixed mice exhibit aversion-resistant drinking and to leverage behavioral analysis techniques available in head-fixture to relate non-consummatory behaviors to aversion-resistant drinking. We assessed aversion-resistant drinking in head-fixed female and male C57BL/6J mice. We adulterated 20% (v/v) alcohol with varying concentrations of the bitter tastant quinine to measure the degree to which mice would continue to drink despite this aversive stimulus. We recorded high-resolution video of the mice during head-fixed drinking, tracked body parts with machine vision tools, and analyzed body movements in relation to consumption. Female and male head-fixed mice exhibited heterogenous levels of aversion-resistant drinking. Additionally, non-consummatory behaviors, such as paw movement and snout movement, were related to the intensity of aversion-resistant drinking. These studies demonstrate that head-fixed mice exhibit aversion-resistant drinking and that non-consummatory behaviors can be used to assess perceived aversiveness in this paradigm. Furthermore, these studies lay the groundwork for future experiments that will utilize advanced electrophysiological techniques to record from large populations of neurons during aversion-resistant drinking to understand the neurocomputational processes that drive this clinically relevant behavior.

One binge-type cycle of alcohol plus ketamine exposure induces emotional-like disorders associated with oxidative damage in adolescent female rats

Drug abuse is a global public health problem among adolescents, with alcohol often used in association with other psychotropic drugs, such as ketamine. Considering the scarcity of evidence, this study aimed to investigate emotional behavioral effects induced by ethanol plus ketamine co-abuse, as well as oxidative biochemistry, and neurotrophic mediator in the prefrontal cortex and hippocampus in the early withdrawal of adolescent female rats. Animals were divided into control, ethanol, ketamine, and ethanol plus ketamine groups. The protocol administration was performed for 3 consecutive days (binge-like pattern). Behavioral assays of open field, elevated plus maze, and forced swim test were performed. After that, the prefrontal cortex and hippocampus were collected to evaluate oxidative biochemistry (reactive oxygen species-ROS; Antioxidant capacity against peroxyl radicals-ACAP; and lipid peroxidation). We found that isolated or combined ethanol and ketamine exposure displayed anxiety- and depressive-like profile, in a non-synergistically manner during early withdrawal. However, oxidative damage was aggravated in the co-administered animals than in isolated exposed subjects. We concluded that ethanol plus ketamine co-abuse may intensify oxidative damage in the hippocampus and prefrontal cortex in the early withdrawal of adolescent female rats, which was not reflected in the emotional behavioral phenotype. DATA AVAILABILITY STATEMENT: The datasets used and/or analyzed during the current investigation are available upon reasonable request from the corresponding author.

A critical review of front-loading: A maladaptive drinking pattern driven by alcohol's rewarding effects

Front-loading is a drinking pattern in which alcohol intake is skewed toward the onset of reward access. This phenomenon has been reported across several different alcohol self-administration protocols in a wide variety of species, including humans. The hypothesis of the current review is that front-loading emerges in response to the rewarding effects of alcohol and can be used to measure the motivation to consume alcohol. Alternative or additional hypotheses that we consider and contrast with the main hypothesis are that: (1) front-loading is directed at overcoming behavioral and/or metabolic tolerance and (2) front-loading is driven by negative reinforcement. Evidence for each of these explanations is reviewed. We also consider how front-loading has been evaluated statistically in previous research and make recommendations for defining this intake pattern in future studies. Because front-loading may predict long-term maladaptive alcohol drinking patterns leading to the development of alcohol use disorder (AUD), several future directions are proposed to elucidate the relationship between front-loading and AUD.

Rewarding and Antidepressant Properties of Ketamine and Ethanol: Effects on the Brain-Derived Neurotrophic Factor and TrkB and p75NTR Receptors

There is a high level of comorbidity between depression and alcohol use disorder. Subanesthetic doses of ketamine induce short-acting and enduring antidepressant effects after a single or a few administrations. Considering such comorbidity, we assessed, in Swiss male mice, if ketamine-induced antidepressant-like effects would alter ethanol's rewarding effects; and, if ethanol pretreatment would alter the rewarding and antidepressant effects of ketamine. The role of the brain-derived neurotrophic factor (BDNF) and its high and low affinity receptors TrkB and p75NTR, respectively, in both reward and depression-related behaviors is well established. The present study assessed, in outbred Swiss male mice, the expression of these proteins in the prefrontal cortex and hippocampus. Ketamine did not alter the development of ethanol-induced conditioned place preference (CPP), yet ethanol inhibited the expression of CPP induced by 50 mg/kg ketamine. The antidepressant action of 50 mg/kg ketamine was attenuated after repeated treatment (i.e., developed tolerance), an effect blocked by ethanol preexposure; ethanol also inhibited the antidepressant effect of 30 mg/kg ketamine. Ketamine (50 mg/kg) and Ethanol-Ketamine (50 mg/kg) groups showed lower levels of 145 kDa TrkB in the hippocampus than Saline-treated group. Ethanol-Ketamine (50 mg/kg) decreased the hippocampal expression of p75NTR compared to Saline-Saline and Saline-Ethanol groups. Ketamine (50 mg/kg) induced hippocampal downregulation of 145 kDa TrkB may contribute to ketamine-induced antidepressant tolerance. Likewise, a relationship between low hippocampal levels of p75NTR in the Ethanol-Ketamine (50 mg/kg) and ketamine-induced CPP blockade may be considered. The findings underscore potential ethanol-ketamine interactions likely to undermine ketamine putative antidepressant effects.