Did Stress Prevalence Among Adolescents in Scandinavia Change from 2000 to 2019? A literature review.

Background: Prolonged stress is a risk factor for developing mental illness and stress-related diseases. As there has been an increase in self-reported psychological symptoms and diagnosis of mental illness among Scandinavian adolescents, more knowledge of stress prevalence in this age group is needed. Aim: This literature review will investigate a possible increase in stress prevalence among Scandinavian adolescents, aged 13-18, between the years 2000 and 2019. Methods: A systematic literature search was conducted in the PubMed and PsycInfo databases. In addition, a grey literature search was conducted to find relevant surveys and reports. Altogether, nine papers and nine surveys, and reports containing relevant data were identified, assessed for risk of bias, and included in the analysis. Results: The results show higher stress scores among the older participants in the age group 13-18 years and a gender difference, where girls score higher than boys. The literature neither supports nor rejects the hypothesis that stress levels have increased among adolescents in Scandinavia, from year 2000 to 2019. Only two of the included studies used a validated stress questionnaire and there was a substantial risk of non-response bias. Therefore, the existing literature is considered insufficient to determine if there has been an increase in stress over time. A majority of the papers, surveys, and reports had moderate risk of bias. Conclusions: Further research using validated stress questionnaires in representative populations is needed to investigate changes in stress prevalence among Scandinavian adolescents. Also, the age and gender difference in stress prevalence among 13-18-year-olds may be of relevance for planning preventive interventions to reduce stress.

Inactivation of the cholinergic M4 receptor results in a disinhibited endophenotype predicting alcohol use.

The muscarinic cholinergic M4 receptor subtype (M4 mAChR) is densely expressed in brain areas known to be involved in the reinforcing effects of drugs of abuse and we were the first to show that mice lacking M4 mAChRs exhibit elevated operant responding for alcohol and reduced capacity to extinguish this alcohol-seeking behaviour. Here we explore possible underlying determinants of this phenotype. We subjected M4 mAChR knockout mice and their littermate wildtype controls to tests of spontaneous activity, learning and memory, novelty seeking, as well as anxiety and examined the relationship of a newly discovered "disinhibited" endophenotype of these mice with voluntary alcohol consumption and relapse. We found a positive correlation between "disinhibited" behaviour on the plus maze and alcohol preference as well as relapse to alcohol drinking after a period of abstinence. Taken together, these data point to M4 mAChRs as a potential target for improved treatment strategies for alcohol use disorder. This receptor should be further investigated for its involvement in modulating behavioural inhibition in relation to loss of control over consumption of alcohol.

The role of glucagon-like peptide 1 (GLP-1) in addictive disorders.

Drug, alcohol and tobacco use disorders are a global burden affecting millions of people. Despite decades of research, treatment options are sparse or missing, and relapse rates are high. Glucagon-like peptide 1 (GLP-1) is released in the small intestine, promotes blood glucose homeostasis, slows gastric emptying and reduces appetite. GLP-1 receptor agonists approved for treating Type 2 diabetes mellitus and obesity have received attention as a potential anti-addiction treatment. Studies in rodents and non-human primates have demonstrated a reduction in intake of alcohol and drugs of abuse, and clinical trials have been initiated to investigate whether the preclinical findings can be translated to patients. This review will give an overview of current findings and discuss the possible mechanisms of action. We suggest that effects of GLP-1 in alcohol and substance use disorders is mediated centrally, at least partly through dopamine signalling, but precise mechanisms are still to be uncovered. LINKED ARTICLES: This article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc.

Proinflammatory biomarkers are associated with prediabetes in patients with schizophrenia.

BACKGROUND: Treatment with antipsychotics is associated with an increased risk of type 2 diabetes mellitus (T2D), and increased levels of inflammatory biomarkers are present in patients with T2D. We previously demonstrated that the glucagon-like peptide-1 receptor agonist liraglutide significantly reduced glucometabolic disturbances and body weight in prediabetic, overweight/obese schizophrenia-spectrum disorder patients treated with clozapine or olanzapine. This study aims to assess the involvement of cytokines in the therapeutic effects of liraglutide. METHODS: Serum concentrations of 10 cytokines (interferon-γ [IFN-γ], tumor necrosis factor-α, interleukin 1ß [IL-1ß], IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, and IL-13) from fasting prediabetic and normal glucose-tolerant (NGT) patients with schizophrenia-spectrum disorders were measured using multiplexed immunoassays. Prediabetic patients were randomized to 16 weeks of treatment with liraglutide or placebo, and cytokines were measured again at the end of the treatment. RESULTS: IFN-γ (1.98 vs 1.17 pg/ml, P = .001), IL-4 (0.02 vs 0.01 pg/ml, P < .001), and IL-6 (0.73 vs 0.46 pg/ml, P < .001) were significantly higher in prediabetic (n = 77) vs NGT patients (n = 31). No significant changes in cytokine levels following treatment with liraglutide (n = 37) vs placebo (n = 40) were found. CONCLUSION: Prediabetic vs NGT patients with schizophrenia treated with clozapine or olanzapine had increased serum levels of several proinflammatory cytokines, further substantiating the link between inflammation and T2D. Treatment with liraglutide did not affect the investigated cytokines. Further testing of these findings in larger numbers of individuals is needed.

Disruption of the PDZ domain-binding motif of the dopamine transporter uniquely alters nanoscale distribution, dopamine homeostasis, and reward motivation.

The dopamine (DA) transporter (DAT) is part of a presynaptic multiprotein network involving interactions with scaffold proteins via its C-terminal PDZ domain-binding sequence. Using a mouse model expressing DAT with mutated PDZ-binding sequence (DAT-AAA), we previously demonstrated the importance of this binding sequence for striatal expression of DAT. Here, we show by application of direct stochastic reconstruction microscopy not only that the striatal level of transporter is reduced in DAT-AAA mice but also that the nanoscale distribution of this transporter is altered with a higher propensity of DAT-AAA to localize to irregular nanodomains in dopaminergic terminals. In parallel, we observe mesostriatal DA adaptations and changes in DA-related behaviors distinct from those seen in other genetic DAT mouse models. DA levels in the striatum are reduced to ∼45% of that of WT, accompanied by elevated DA turnover. Nonetheless, fast-scan cyclic voltammetry recordings on striatal slices reveal a larger amplitude and prolonged clearance rate of evoked DA release in DAT-AAA mice compared with WT mice. Autoradiography and radioligand binding show reduced DA D2 receptor levels, whereas immunohistochemistry and autoradiography show unchanged DA D1 receptor levels. In behavioral experiments, we observe enhanced self-administration of liquid food under both a fixed ratio of one and progressive ratio schedule of reinforcement but a reduction compared with WT when using cocaine as reinforcer. In summary, our data demonstrate how disruption of PDZ domain interactions causes changes in DAT expression and its nanoscopic distribution that in turn alter DA clearance dynamics and related behaviors.

The effect of erythropoietin on electroconvulsive stimulation induced cognitive impairment in rats.

Electroconvulsive therapy (ECT) is the most effective and fast-acting treatment for severe depression but associated with troublesome cognitive side-effects. Systemically administered erythropoietin (EPO) crosses the blood-brain-barrier and is a promising treatment for cognitive dysfunction in a wide array of neuropsychiatric and neurological disorders. In this study we trained rats to locate a submerged platform in a water maze and then subjected them to electroconvulsive stimulations (ECS, the rodent equivalent to ECT) and EPO treatment. We then analysed their ability to remember and relearn the location of the platform. In addition, we examined "wall-clinging" (thigmotaxis), a behavioural indicator of stress. ECS caused significant deficit in a probe trial administered after three weeks (nine stimulations) as well as one week (six stimulations) of treatment, indicative of induction of retrograde amnesia. ECS had no effect on relearning of the water maze task or performance in a subsequent probe trial. EPO treatment did not ameliorate the ECS-induced retrograde amnesia, but after nine ECS stimulations the animals that had received EPO relearned the position of the hidden platform faster than the animals that had not. We also found EPO to decrease "wall-clinging" behaviour, suggesting an effect of EPO on the stress response in rats. Thus, we establish the Morris Water Maze as a suitable model for ECS-induced memory loss in rats and provide some evidence for potential beneficial effects of EPO.

G protein-coupled receptor signaling in VTA dopaminergic neurons bidirectionally regulates the acute locomotor response to amphetamine but does not affect behavioral sensitization.

Amphetamine (AMPH) acts as a substrate of the dopamine transporter (DAT) and causes a dramatic increase in extracellular dopamine (DA). Upon entering DA neurons, AMPH promotes DA efflux via DAT through a mechanism implicating depletion of DA from vesicular stores, activation of kinase pathways and transporter phosphorylation. Despite the role of intracellular signaling for AMPH action, it remains elusive how the response to AMPH is affected in vivo by metabotropic regulation via G protein coupled receptor signaling pathways. Here, we show by employment of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) that the acute hyperlocomotor response to AMPH is bidirectionally regulated by metabotropic input to VTA DA neurons with a markedly enhanced response upon activation of a Gs-coupled pathway and a markedly decreased locomotor response upon activation of a Gi-coupled pathway. The unique mechanism of action for AMPH was underlined by the absence of an effect of Gs activation on the locomotor response to the DAT inhibitor cocaine. Regardless of the profound effect on the acute AMPH response, repeated Gs activation or Gi activation did not affect development of AMPH sensitization. Furthermore, activation of a Gs-pathway or activation of a Gi-pathway in DA neurons did not have any effect on the AMPH-induced locomotor response in the AMPH sensitized mice. This suggests induction of alterations in DA neuronal functions that overrule the stimulatory or inhibitory effect of metabotropic input seen in drug-naïve mice. The data thereby underline the remarkable strength of maladaptive changes that occur upon intake of strong psychostimulants. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

Glucagon-Like Peptide-1 Receptor Agonist Treatment Does Not Reduce Abuse-Related Effects of Opioid Drugs.

Dependence on opioids and the number of opioid overdose deaths are serious and escalating public health problems, but medication-assisted treatments for opioid addiction remain inadequate for many patients. Glucagon-like pepide-1 (GLP-1) is a gut hormone and neuropeptide with actions in peripheral tissues and in the brain, including regulation of blood glucose and food intake. GLP-1 analogs, which are approved diabetes medications, can reduce the reinforcing and rewarding effects of alcohol, cocaine, amphetamine, and nicotine in rodents. Investigations on effects of GLP-1 analogs on opioid reward and reinforcement have not been reported. We assessed the effects of the GLP-1 receptor agonist Exendin-4 (Ex4) on opioid-related behaviors in male mice, i.e., morphine-conditioned place preference (CPP), intravenous self-administration (IVSA) of the short-acting synthetic opioid remifentanil, naltrexone-precipitated morphine withdrawal, morphine analgesia (male and female mice), and locomotor activity. Ex4 treatment had no effect on morphine-induced CPP, withdrawal, or hyperlocomotion. Ex4 failed to decrease remifentanil self-administration, if anything reinforcing effects of remifentanil appeared increased in Ex4-treated mice relative to saline. Ex4 did not significantly affect analgesia. In contrast, Ex4 dose dependently decreased oral alcohol self-administration, and suppressed spontaneous locomotor activity. Taken together, Ex4 did not attenuate the addiction-related behavioral effects of opioids, indicating that GLP-1 analogs would not be useful medications in the treatment of opioid addiction. This difference between opioids and other drug classes investigated to date may shed light on the mechanism of action of GLP-1 receptor treatment in the addictive effects of alcohol, central stimulants, and nicotine.

Markers of HPA-axis activity and nucleic acid damage from oxidation after electroconvulsive stimulations in rats.

OBJECTIVE: Oxidative stress has been suggested to increase after electroconvulsive therapy (ECT), a treatment which continues to be the most effective for severe depression. Oxidative stress could potentially be mechanistically involved in both the therapeutic effects and side effects of ECT. METHODS: We measured sensitive markers of systemic and central nervous system (CNS) oxidative stress on DNA and RNA (urinary 8-oxodG/8-oxoGuo, cerebrospinal fluid 8-oxoGuo, and brain oxoguanine glycosylase mRNA expression) in male rats subjected to electroconvulsive stimulations (ECS), an animal model of ECT. Due to the previous observations that link hypothalamic-pituitary-adrenal (HPA)-axis activity and age to DNA/RNA damage from oxidation, groups of young and middle-aged male animals were included, and markers of HPA-axis activity were measured. RESULTS: ECS induced weight loss, increased corticosterone (only in middle-aged animals), and decreased cerebral glucocorticoid receptor mRNA expression, while largely leaving the markers of systemic and CNS DNA/RNA damage from oxidation unaltered. CONCLUSION: These results suggest that ECS is not associated with any lasting effects on oxidative stress on nucleic acids neither in young nor middle-aged rats.

Initial rewarding effects of cocaine and amphetamine assessed in a day using the single-exposure place preference protocol.

In rodents, only a single dose of cocaine or amphetamine is required to cause a marked increase in extracellular dopamine, induce hyperlocomotion and cause persistent plasticity changes within dopaminergic neurons of the ventral tegmental area (VTA). The initial drug experience is suggested to predict vulnerability of developing addiction, but only few studies have assessed the perception of reward accompanying this initial exposure. We recently presented an approach to assess the initial rewarding effects of cocaine in mice with a single-exposure place preference (sePP) protocol, avoiding repeated drug injections. Here, we demonstrate a condensed version of the sePP, allowing assessment of initial subjective reward-perception within a day. By using this protocol, we demonstrate that a single exposure to both cocaine and amphetamine is sufficient to induce place preference. Furthermore, we use chemogenetics ( Designer Receptors Exclusively Activated by Designer Drugs [DREADD]) to show that both inhibitory and stimulatory modulation of VTA DA signalling disrupts cocaine-induced place preference in the condensed sePP. Our findings support the presence of initial reward-perception of both cocaine and amphetamine, and the formation of drug-context association. In addition, our data support that VTA DA signalling prior to drug exposure affects either reward-perception or the time during which associations are formed, thereby preventing induction of cocaine-induced place preference in the sePP. The easy and timesaving sePP protocol should form a critical basis for further deciphering the complex mechanisms underlying the progression from the initial drug experience to escalating drug intake and addiction.

Increased oxidation of RNA despite reduced mitochondrial respiration after chronic electroconvulsive stimulation of rat brain tissue.

Major depressive disorder (MDD) affects 350 million people worldwide and is a serious socio-economic burden. The most efficient treatment of MDD is electroconvulsive therapy (ECT), which has been shown to influence the oxidative status believed to be part of the pathophysiology of MDD. We investigated the effects of chronic electroconvulsive stimulation (ECS) on mitochondrial respiration and mitochondrial hydrogen peroxide production, RNA oxidation, and the content of mitochondria in the piriform cortex of the rat. We found reductions of mitochondrial respiration in respiratory states 2 and 3 by 33% and 32%, respectively, and a 23% reduction in electron transfer capacity. RNA oxidation, as measured by 8-oxo-7,8-dihydroguanosine, was increased by 58%, while mitochondrial production of H2O2 was unaffected. The increased oxidative stress may thus be ascribed to extra-mitochondrial sources.

Locomotor- and Reward-Enhancing Effects of Cocaine Are Differentially Regulated by Chemogenetic Stimulation of Gi-Signaling in Dopaminergic Neurons.

Dopamine plays a key role in the cellular and behavioral responses to drugs of abuse, but the implication of metabotropic regulatory input to dopaminergic neurons on acute drug effects and subsequent drug-related behavior remains unclear. Here, we used chemogenetics [Designer Receptors Exclusively Activated by Designer Drugs (DREADDs)] to modulate dopamine signaling and activity before cocaine administration in mice. We show that chemogenetic inhibition of dopaminergic ventral tegmental area (VTA) neurons differentially affects locomotor and reward-related behavioral responses to cocaine. Stimulation of Gi-coupled DREADD (hM4Di) expressed in dopaminergic VTA neurons persistently reduced the locomotor response to repeated cocaine injections. An attenuated locomotor response was seen even when a dual-viral vector approach was used to restrict hM4Di expression to dopaminergic VTA neurons projecting to the nucleus accumbens. Surprisingly, despite the attenuated locomotor response, hM4Di-mediated inhibition of dopaminergic VTA neurons did not prevent cocaine sensitization, and the inhibitory effect of hM4Di-mediated inhibition was eliminated after withdrawal. In the conditioned place-preference paradigm, hM4Di-mediated inhibition did not affect cocaine-induced place preference; however, the extinction period was extended. Also, hM4Di-mediated inhibition had no effect on preference for a sugar-based reward over water but impaired motivation to work for the same reward in a touchscreen-based motivational assay. In addition, to support that VTA dopaminergic neurons operate as regulators of reward motivation toward both sugar and cocaine, our data suggest that repeated cocaine exposure leads to adaptations in the VTA that surmount the ability of Gi-signaling to suppress and regulate VTA dopaminergic neuronal activity.

PICK1-Deficient Mice Exhibit Impaired Response to Cocaine and Dysregulated Dopamine Homeostasis.

Protein interacting with C-kinase 1 (PICK1) is a widely expressed scaffold protein known to interact via its PSD-95/discs-large/ZO-1 (PDZ)-domain with several membrane proteins including the dopamine (DA) transporter (DAT), the primary target for cocaine's reinforcing actions. Here, we establish the importance of PICK1 for behavioral effects observed after both acute and repeated administration of cocaine. In PICK1 knock-out (KO) mice, the acute locomotor response to a single injection of cocaine was markedly attenuated. Moreover, in support of a role for PICK1 in neuroadaptive changes induced by cocaine, we observed diminished cocaine intake in a self-administration paradigm. Reduced behavioral effects of cocaine were not associated with decreased striatal DAT distribution and most likely not caused by the ∼30% reduction in synaptosomal DA uptake observed in PICK1 KO mice. The PICK1 KO mice demonstrated preserved behavioral responses to DA receptor agonists supporting intact downstream DA receptor signaling. Unexpectedly, we found a prominent increase in striatal DA content and levels of striatal tyrosine hydroxylase (TH) in PICK1 KO mice. Chronoamperometric recordings showed enhanced DA release in PICK1 KO mice, consistent with increased striatal DA pools. Viral-mediated knock-down (KD) of PICK1 in cultured dopaminergic neurons increased TH expression, supporting a direct cellular effect of PICK1. In summary, in addition to demonstrating a key role of PICK1 in mediating behavioral effects of cocaine, our data reveal a so far unappreciated role of PICK1 in DA homeostasis that possibly involves negative regulation of striatal TH levels.

Erythropoietin prevents the effect of chronic restraint stress on the number of hippocampal CA3c dendritic terminals-relation to expression of genes involved in synaptic plasticity, angiogenesis, inflammation, and oxidative stress in male rats.

Stress-induced allostatic load affects a variety of biological processes including synaptic plasticity, angiogenesis, oxidative stress, and inflammation in the brain, especially in the hippocampus. Erythropoietin (EPO) is a pleiotropic cytokine that has shown promising neuroprotective effects. Recombinant human EPO is currently highlighted as a new candidate treatment for cognitive impairment in neuropsychiatric disorders. Because EPO enhances synaptic plasticity, attenuates oxidative stress, and inhibits generation of proinflammatory cytokines, EPO may be able to modulate the effects of stress-induced allostatic load at the molecular level. The aim of this study was therefore to investigate how EPO and repeated restraint stress, separately and combined, influence (i) behavior in the novelty-suppressed feeding test of depression/anxiety-related behavior; (ii) mRNA levels of genes encoding proteins involved in synaptic plasticity, angiogenesis, oxidative stress, and inflammation; and (iii) remodeling of the dendritic structure of the CA3c area of the hippocampus in male rats. As expected, chronic restraint stress lowered the number of CA3c apical dendritic terminals, and EPO treatment reversed this effect. Interestingly, these effects seemed to be mechanistically distinct, as stress and EPO had differential effects on gene expression. While chronic restraint stress lowered the expression of spinophilin, tumor necrosis factor α, and heat shock protein 72, EPO increased expression of hypoxia-inducible factor-2α and lowered the expression of vascular endothelial growth factor in hippocampus. These findings indicate that the effects of treatment with EPO follow different molecular pathways and do not directly counteract the effects of stress in the hippocampus.

The Circadian Oscillator of the Cerebral Cortex: Molecular, Biochemical and Behavioral Effects of Deleting the Arntl Clock Gene in Cortical Neurons.

A molecular circadian oscillator resides in neurons of the cerebral cortex, but its role is unknown. Using the Cre-LoxP method, we have here abolished the core clock gene Arntl in those neurons. This mouse represents the first model carrying a deletion of a circadian clock component specifically in an extrahypothalamic cell type of the brain. Molecular analyses of clock gene expression in the cerebral cortex of the Arntl conditional knockout mouse revealed disrupted circadian expression profiles, whereas clock gene expression in the suprachiasmatic nucleus was still rhythmic, thus showing that Arntl is required for normal function of the cortical circadian oscillator. Daily rhythms in running activity and temperature were not influenced, whereas the resynchronization response to experimental jet-lag exhibited minor though significant differences between genotypes. The tail-suspension test revealed significantly prolonged immobility periods in the knockout mouse indicative of a depressive-like behavioral state. This phenotype was accompanied by reduced norepinephrine levels in the cerebral cortex. Our data show that Arntl is required for normal cortical clock function and further give reason to suspect that the circadian oscillator of the cerebral cortex is involved in regulating both circadian biology and mood-related behavior and biochemistry.

Ketogenic Diet Suppresses Alcohol Withdrawal Syndrome in Rats.

BACKGROUND: Alcohol use disorder is underdiagnosed and undertreated, and up to 50% of alcohol-abstinent patients diagnosed with alcohol dependence relapse within the first year of treatment. Current treatments for the maintenance of alcohol abstinence in patients with alcohol use disorder have limited efficacy, and there is an urgent need for novel treatment strategies. Decreased cerebral glucose metabolism and increased brain uptake of acetate were recently reported in heavy drinkers, relative to controls. Given the switch of metabolic fuel from glucose to acetate in the alcohol-dependent brain, we investigated the potential therapeutic benefit of a ketogenic diet in managing alcohol withdrawal symptoms during detoxification. METHODS: Male Sprague Dawley rats fed either ketogenic or regular diet were administered ethanol or water orally, twice daily for 6 days while the diet conditions were maintained. Abstinence symptoms were rated 6, 24, 48, and 72 hours after the last alcohol administration. RESULTS: Maintenance on a ketogenic diet caused a significant decrease in the alcohol withdrawal symptoms' "rigidity" and "irritability." CONCLUSIONS: Our preclinical pilot study suggests that a ketogenic diet may be a novel approach for treating alcohol withdrawal symptoms in humans.

[Erythropoietin treatment may improve cognition in neuropsychiatric disorders].

Cognitive dysfunction is a core feature in a range of neuropsychiatric disorders which reduces patients' workforce capacity - the largest socio-economic cost of these disorders. Nevertheless, there is no clinically available medical treatment with robust and enduring efficacy on cognitive deficits in most neuropsychiatric conditions. Recent research has shown that erythropoietin may have beneficial effects on cognitive dysfunction across neuropsychiatric disorders, including bipolar and unipolar disorders, schizophrenia, Parkinson's disease and multiple sclerosis.

The glucagon-like peptide 1 receptor agonist Exendin-4 decreases relapse-like drinking in socially housed mice.

Glucagon-like peptide-1 (GLP-1) is a gut peptide that regulates food intake and glucose metabolism. GLP-1 is also produced and released in the brain, and GLP-1 receptors are expressed in brain regions important for alcohol and drug reward, and for the development of addiction. GLP-1 receptor agonists can decrease alcohol intake acutely in rodents. However, alcohol use disorder is a chronic condition that requires treatments to be effective in promoting abstinence from excessive alcohol consumption over time. Here, we assessed the effect of daily treatment with the GLP-1 receptor agonist Exendin-4 in an assay of relapse-like drinking in socially housed mice. Male C57BL/6NTac mice were allowed continuous access to alcohol without tastant in the home cage for 37days. Then, alcohol bottles were removed and Exendin-4 (1.5µg/kg/day) or saline was administered subcutaneously for 8days during alcohol deprivation. Treatment continued for 8 additional days after reintroducing access to alcohol. A high-precision automated fluid consumption system was used to monitor intake of alcohol and water, drinking kinetics, and locomotor activity. Exendin-4 prevented the deprivation-induced increase in alcohol intake observed in control mice, without significantly affecting total fluid intake, body weight, or locomotor activity. The reduced alcohol intake was caused by a protracted latency to the first drink of alcohol and a reduced number of drinking bouts, while bout size and duration were not affected. The effect was maintained undiminished throughout the treatment period. These findings support the possible use of GLP-1 receptor agonists in the treatment of alcohol use disorder.

Subjective perception of cocaine reward in mice assessed by a single exposure place preference (sePP) paradigm.

BACKGROUND: The potential of abused drugs to induce addiction and compulsive drug-related behavior is associated with their ability to alter dopamine signaling. Dopamine plays a key role in reward signaling and it has been of great interest to investigate how various drugs of abuse alter reward-related behavior. COMPARISON WITH EXISTING METHODS: In rodents, the rewarding effects of drugs have often been assessed in self-administration or place preference paradigms; both involving repeated drug exposure and weeks of training and testing. NEW METHOD: Our investigation describes a valid approach to assess the initial rewarding effects of cocaine in mice with a single exposure place preference (sePP) paradigm, avoiding repeated drug injections. RESULTS: We present the sePP paradigm with a 3-day protocol to assess the initial rewarding effects of cocaine. Interestingly, only male mice exhibit sePP to cocaine. To assess subsequent drug-related behavior, the protocol was extended by 3days of extinction followed by reinstatement on day 10. CONCLUSION: The sePP paradigm provides a reliable and convenient approach to assess the initial rewarding effects of cocaine, circumventing the need for repeated drug injections. The sePP protocol allows further dissection of the mechanism and influence of initial cocaine exposure on subsequent drug-related behaviors by including extinction and reinstatement. The lack of sePP in female mice may reflect a biologically relevant sex difference in the initial subjective perception of cocaine-induced reward. This could relate to and explain why males and females have been reported to respond differently to cocaine and cocaine-associated cues.